Arylsulfinate salts in initiator systems for polymeric reactions

ABSTRACT

Compositions are provided that that can be used as an initiator system for free radical polymerization reactions. More specifically, the initiator systems include an electron acceptor and an electron donor. The electron donors are arylsulfinate salts having a cation that contains at least one carbon atom and either a positively charged nitrogen atom or a positively charged phosphorus atom. Methods of polymerization are also provided that can be used to prepare polymeric material with the initiator systems. The initiator systems can be thermal initiator systems, photoinitiator systems, or combinations thereof.

TECHNICAL FIELD

Arylsulfinate salts are provided that can be used as electron donors ininitiator systems for free radical polymerization reactions.

BACKGROUND

Free radical polymerization reactions typically have an initiatorsystem. The initiator systems can be based on various chemicalapproaches. For example, free radical polymerization reactions can beinitiated using a three-component photoinitiator system that includes anelectron acceptor, an electron donor, and a sensitizing compound.Alternatively, an electron donor in combination with a sensitizingcompound can be used as a photoinitiator system. Free radicalpolymerization reactions also can be initiated using a two-componentthermal initiator system that includes an electron acceptor and anelectron donor.

In thermally initiated free radical polymerization reactions, anelectron donor usually reacts directly with an electron acceptor toreduce the electron acceptor. The reduced electron acceptor can be aradical that can function as an initiating free radical for thepolymerization reaction. The reaction between the electron donor andacceptor can occur at room temperature or at elevated temperatures. Theelectron acceptor and the electron donor are often kept in separatecontainers (i.e., not mixed together) until polymerization is desired.

In contrast to thermally initiated systems, the components of aphotoinitiator system usually can be mixed together prior to use. In athree-component photoinitiator system that includes an electron donor,electron acceptor and a sensitizing compound, there is typically nodirect reaction between the electron donor and the electron acceptor.Rather, the sensitizing compound usually absorbs actinic radiationresulting in the formation of an excited sensitizing compound. Theelectron donor can donate an electron to the excited sensitizingcompound. That is, the sensitizing compound is reduced and the electrondonor is oxidized. The reduced sensitizing compound is a radical anionthat can donate an electron to an electron acceptor to yield aninitiating free radical for the polymerization reaction. The initiatingfree radical is the reduced electron acceptor. In some instances of athree-component photoinitiator system, the oxidized electron donor is aradical species that also can function as an initiating free radical.

Other photoinitiator systems include a sensitizing compound and anelectron donor but no electron acceptor. The sensitizing compound canabsorb actinic radiation to form an exited sensitizing compound. Theelectron donor can donate an electron to the excited sensitizingcompound resulting in the oxidation of the electron donor. The oxidizedelectron donor is a radical species that functions as an initiating freeradical for polymerization reactions.

SUMMARY

Compositions are provided that include an electron donor and an electronacceptor. More specifically, the electron donor is an arylsulfinatesalt. Methods of polymerization are provided that can be used to preparepolymeric material using a free radical polymerization reaction. Thepolymerization reaction is initiated with a photoinitiator system,thermal initiator system, or combinations thereof.

One aspect of the invention provides a composition that includes anelectron donor and an electron acceptor. The electron donor has anoxidation potential in N,N-dimethylformamide of 0.0 to +0.4 volts versusa silver/silver nitrate reference electrode and includes anarylsulfinate salt having an anion of Formula IAr¹—SO₂ ⁻  Iand having a cation that contains at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom. The Ar¹ group in Formula I is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl. A substituted Ar¹ group can have asubstituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group. Theelectron acceptor has a reduction potential in N,N-dimethylformamide of+0.4 to −1.0 volts versus a silver/silver nitrate reference electrode.The composition can further include a sensitizing compound,ethylenically unsaturated monomers, hydroxy-containing material, orcombinations thereof.

A second aspect of the invention provides a photopolymerization methodthat includes irradiating a photopolymerizable composition with actinicradiation until the photopolymerizable composition gels or hardens. Thephotopolymerizable composition includes an ethylenically unsaturatedmonomer, a sensitizing compound, an electron donor, and an electronacceptor. The sensitizing compound is capable of absorbing a wavelengthof actinic radiation in the range of 250 to 1000 nanometers. Theelectron acceptor has a reduction potential in N,N-dimethylformamide of+0.4 to −1.0 volts versus a silver/silver nitrate reference electrodeand forms a colorless solution when dissolved in an alcohol or anethylenically unsaturated monomer. The electron donor has an oxidationpotential in N,N-dimethylformamide of 0.0 to +0.4 volts versus asilver/silver nitrate reference electrode and includes an arylsulfinatesalt. The arylsulfinate salt has an anion of Formula IAr¹—SO₂ ⁻  Iand a cation that contains at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom. The Ar¹ group in Formula I is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl. A substituted Ar¹ group can have asubstituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group.

A third aspect of the invention provides a method of polymerization thatincludes forming a polymerizable composition and reacting thepolymerizable composition. The polymerizable composition includes anethylenically unsaturated monomer, an electron donor having an oxidationpotential in N,N-dimethylformamide of 0.0 to +0.4 volts versus asilver/silver nitrate reference electrode, and an electron acceptorhaving a reduction potential in N,N-dimethylformamide of +0.4 to −1.0volts versus a silver/silver nitrate reference electrode. The electrondonor is an arylsulfinate salt having an anion of Formula IAr¹—SO₂ ⁻  Iand having a cation that contains at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom. The Ar¹ group in Formula I is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl. A substituted Ar¹ group can have asubstituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present invention. The detaileddescription section that follow more particularly exemplify theseembodiments.

DETAILED DESCRIPTION

Compositions are provided that include an electron donor and an electronacceptor. More specifically, the electron donor is an arylsulfinatesalt. Methods of polymerization are also provided that can be used toprepare polymeric material from a polymerizable composition. Thepolymerizable composition includes an initiator system with anarylsulfinate salt as the electron donor. The initiator system can be athermal initiator system, photoinitiator system, or combinationsthereof.

Definitions

As used herein, the terms “a”, “an”, and “the” are used interchangeablywith “at least one” to mean one or more of the elements being described.

As used herein, the term “actinic radiation” refers to electromagneticradiation capable of producing photochemical activity.

As used herein, the term “acyl” refers to a monovalent group of formula—(CO)R^(a) where R^(a) is an alkyl or aryl group.

As used herein, the term “alkenyl” refers to a monovalent radical of analkene (i.e., an alkene is an aliphatic compound having at least onecarbon-carbon double bond).

As used herein, the term “alkoxy” refers to a group of formula —OR whereR is an alkyl group. Examples include methoxy, ethoxy, propoxy, butoxy,and the like.

As used herein, the term “alkoxycarbonyl” refers to a monovalent groupof formula —(CO)OR where R is an alkyl group. An example isethoxycarbonyl.

As used herein, the term “alkoxysulfonyl” refers to a monovalent grouphaving the formula —SO₃R where R is an alkyl group.

As used herein, the term “alkyl” refers to a monovalent radical of analkane. The alkyl can be linear, branched, cyclic, or combinationsthereof and typically contains 1 to 30 carbon atoms. In someembodiments, the alkyl group contains 1 to 20, 1 to 14, 1 to 10, 4 to10, 4 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groupsinclude, but are not limited to methyl, ethyl, n-propyl, isopropyl,n-butyl, tert-butyl, isobutyl, n-pentyl, n-hexyl, cyclohexyl, n-octyl,n-heptyl, and ethylhexyl.

As used herein, the term “alkylsulfonyl” refers to a monovalent group offormula —SO₂R where R is an alkyl group.

As used herein, the term “alkynyl” refers to a monovalent radical of analkyne (i.e., an alkyne is an aliphatic compound having at least onecarbon-carbon triple bond).

As used herein, the term “amino” refers to a monovalent group of formula—NR^(b) ₂ where each R^(b) is independently a hydrogen, alkyl, or arylgroup. In a primary amino group, each R^(b) group is hydrogen. In asecondary amino group, one of the R^(b) groups is hydrogen and the otherR^(b) group is either an alkyl or aryl. In a tertiary amino group, bothof the R^(b) groups are an alkyl or aryl.

As used herein, the term “aminocarbonyl” refers to a monovalent group offormula —(CO)NR^(b) ₂ where each R^(b) is independently a hydrogen,alkyl, or aryl.

As used herein, the term “aromatic” refers to both carbocyclic aromaticcompounds or groups and heteroaromatic compounds or groups. Acarbocyclic aromatic compound is a compound that contains only carbonatoms in an aromatic ring structure. A heteroaromatic compound is acompound that contains at least one heteroatom selected from S, O, N, orcombinations thereof in an aromatic ring structure.

As used herein, the term “aryl” refers to a monovalent aromaticcarbocyclic radical. The aryl can have one aromatic ring or can includeup to 5 carbocyclic ring structures that are connected to or fused tothe aromatic ring. The other ring structures can be aromatic,non-aromatic, or combinations thereof. Examples of aryl groups include,but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl,acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl,perylenyl, and fluorenyl.

As used herein, the term “aryloxy” refers to a monovalent group offormula —OAr where Ar is an aryl group.

As used herein, the term “aryloxycarbonyl” refers to a monovalent groupof formula —(CO)OAr where Ar is an aryl group.

As used herein, the term “aryloxysulfonyl” refers to a monovalent grouphaving the formula —SO₃Ar where Ar is an aryl group.

As used herein, the term “azo” refers to a divalent group of formula—N═N—.

As used herein, the term “carbonyl” refers to a divalent group offormula —(CO)— where the carbon atom is connected to the oxygen atom bya double bond.

As used herein, the term “carboxy” refers to a monovalent group offormula —(CO)OH.

As used herein, the term “conjugated” refers to unsaturated compoundshaving at least two carbon-carbon double or triple bonds withalternating carbon-carbon single bonds and carbon-carbon double ortriple bonds.

As used herein, the term “cyano” refers to a group of formula —CN.

As used herein, the term “dialkylphosphonato” refers to a group offormula —(PO)(OR)₂ where R is an alkyl. As used herein the formula“(PO)” indicates that the phosphorus atom is attached to an oxygen atomwith a double bond.

As used herein, the term “diarylphosphonato” refers to a group offormula —(PO)(OAr)₂ where Ar is an aryl.

As used herein, the term “electron donating” refers to a substituentthat can donate electrons. Suitable examples include, but are notlimited to, a primary amino, secondary amino, tertiary amino, hydroxy,alkoxy, aryloxy, alkyl, or combinations thereof.

As used herein, the term “electron withdrawing” refers to a substituentthat can withdraw electrons. Suitable examples include, but are notlimited to, a halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy,alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo,alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl,azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato,aminocarbonyl, or combinations thereof.

As used herein, the term “fluoroalkyl” refers to an alkyl group that hasat least one hydrogen atom replaced with a fluorine atom.

As used herein, the term “formyl” refers to a monovalent group offormula —(CO)H where the carbon is attached to the oxygen atom with adouble bond.

As used herein, the term “halo” refers to a halogen group (i.e., F, Cl,Br, or I). In some embodiments, the halo group is F or Cl.

As used herein, the term “halocarbonyl” refers to a monovalent group offormula —(CO)X where X is a halogen group (i.e., F, Cl, Br, or I).

As used herein, the term “heteroaryl” refers to a monovalent radicalhaving a five to seven member aromatic ring that includes one or moreheteroatoms independently selected from S, O, N, or combinations thereofin the ring. Such a heteroaryl ring can be connected to or fused to upto five ring structures that are aromatic, aliphatic, or combinationsthereof. Examples of heteroaryl groups include, but are not limited to,quinolinyl, isoquinolinyl, quinazolinyl, quinoxalinyl, cinnolinyl,benzofuranyl, benzomercaptophenyl, benzoxazolyl, benzothiazolyl,benzimidazolyl, indolyl, phthalazinyl, benzothiadiazolyl,benzotriazinyl, phenazinyl, phenanthridinyl, acridinyl, and indazolyl,and the like. A heteroaryl is a subset of a heterocyclic group.

As used herein, the term “heterocyclic” refers to a monovalent radicalhaving a ring structure that is saturated or unsaturated and thatincludes one or more heteroatoms independently selected from S, O, N, orcombinations thereof in the ring. The heterocyclic group can be a singlering, bicyclic, or can be fused to another cyclic or bicyclic group. Thefused cyclic or bicyclic group can be saturated or unsaturated and canbe carbocyclic or contain heteroatoms.

As used herein, the term “hydroxy” refers to a group of formula —OH.

As used herein, the term “mercapto” refers to a group of formula —SH.

As used herein, the term “perfluoroalkyl” refers to an alkyl group thathas all the hydrogen atoms replaced with fluorine atoms. Aperfluoroalkyl is a subset of a fluoroalkyl.

As used herein, the term “perfluoroalkylsulfonyl” refers to a monovalentgroup of formula —SO₂R_(f) where R_(f) is a perfluoroalkyl.

As used herein, the term “polymerization” refers to forming a higherweight material from monomer or oligomers. The polymerization reactionalso can involve a cross-linking reaction.

As used herein when referring to a composition containing an initiatorsystem and polymerizable material, the term “self-stable” means that thecomposition can be stored for at least one day without any visible gelformation at room temperature (i.e., 20° C. to 25° C.).

As used herein when referring to a compound, the term “oxidativestability” refers to the length of time needed to oxidize 50 weightpercent of the compound (t_(1/2)) at room temperature (i.e., 20° C. to25° C.) which can be calculated using pseudo-first order kinetics asdescribed in K. A. Connors, Chemical Kinetics: The Study of ReactionRates in Solution, Chapter 2, VCH, New York, 1990.

As used herein, the term “sulfo” refers to a group having the formula—SO₃H.

Compositions

A variety of materials are known for use as an electron donor ininitiator systems for polymerization reactions. However, some of thesematerials have limited solubility in ethylenically unsaturated monomers.Further, some of these materials have limited oxidative stability,shelf-stability, or combinations thereof.

One aspect of the invention provides a composition that includes anelectron donor and an electron acceptor. More specifically, the electrondonor includes an arylsulfinate salt. The compositions can be used asinitiator systems for free radical polymerization reactions. Theinitiator systems can be used in photopolymerization methods, thermalpolymerization methods, or combinations thereof.

The electron donor has an oxidation potential in N,N-dimethylformamideof 0.0 to +0.4 volts versus a silver/silver nitrate reference electrodeand is an arylsulfinate salt having an anion of Formula IAr¹—SO₂ ⁻  Iand having a cation that contains at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom. The Ar¹ group in Formula I is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl. A substituted Ar¹ group can have asubstituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group. Theelectron acceptor has a reduction potential in N,N-dimethylformamide of+0.4 to −1.0 volts versus a silver/silver nitrate reference electrode.

The electron donor is selected to have an oxidation potential and theelectron acceptor is selected to have a reduction potential in a statedrange. The oxidation and reduction potentials can be determined usingcyclic voltammetry. As described herein, the oxidation and reductionpotentials are measured by dissolving the compound of interest in anon-aqueous solvent (i.e., N,N-dimethylformamide) containing asupporting electrolyte (i.e., 0.1 moles/liter tetrabutylammoniumhexafluorophosphate). The resulting solution is purged with an inert gassuch as argon. A three-electrode configuration is used that includes aworking electrode (i.e., a glassy carbon electrode), a referenceelectrode (i.e., a silver wire in a 0.01 moles/liter of silver nitratedissolved in acetonitrile), and a counter electrode (i.e., a platinumwire). The oxidation or reduction potential is the voltage correspondingto the maximum current for the oxidation or reduction reaction.

One component of the composition is the electron donor. The electrondonor is an arylsulfinate salt. The arylsulfinate salt is typicallysoluble in monomers capable of undergoing free radical polymerizationreactions and in a variety of non-polar and polar solvents. As usedherein, the term “soluble” refers to a compound that can be dissolved inan amount at least equal to 0.05 moles/liter, at least equal to 0.07moles/liter, at least equal to 0.08 moles/liter, at least equal to 0.09moles/liter, or at least equal to 0.1 moles/liter in a given materialsuch as a solvent or monomer.

In some arylsulfinate salts, the Ar¹ group is a substituted phenyl or anunsubstituted or substituted C₇₋₃₀ aryl group having a carbocyclicaromatic ring. The aryl group can have a single carbocyclic aromaticring or can have additional carbocyclic rings that are fused orconnected to the carbocyclic aromatic ring. Any fused or connected ringscan be saturated or unsaturated. The aryl often contains up to 5 rings,up to 4 rings, up to 3 rings, up to 2 rings, or one ring. The aryl groupusually has up to 30 carbon atoms, up to 24 carbon atoms, up to 18carbon atoms, up to 12 carbon atoms, or 6 carbon atoms. Examples of arylgroups having a single ring or multiple fused rings include, but are notlimited to, phenyl, anthryl, naphthyl, acenaphthyl, phenanthryl,phenanthrenyl, perylenyl, and anthracenyl. A single bond, methylenegroup (i.e., —C(R^(b))₂— where each R^(b) is independently hydrogen,alkyl, or aryl), carbonyl group (i.e., —(CO)—), or combinations thereofcan connect multiple rings. Examples of aryl groups having multipleconnected rings include, but are not limited to, anthraquinonyl,anthronyl, biphenyl, terphenyl, 9,10-dihydroanthracenyl, and fluorenyl.

In other arylsulfinate salts, the Ar¹ group in Formula I can be anunsubstituted or substituted heteroaryl that has a five to seven memberaromatic ring that contains one or more heteroatoms independentlyselected from S, O, N, or combinations thereof in the ring. Theheteroaryl can have a single ring or can have multiple rings connectedor fused together. Any additional connected or fused rings can becarbocyclic or contain a heteroatom and can be saturated or unsaturated.The heteroaryl group often has up to 5 rings, up to 4 rings, up to 3rings, up to 2 rings, or one ring. The heteroaryl typically contains upto 30 carbon atoms. In some embodiments, the heteroaryl contains up to20 carbon atoms, up to 10 carbon atoms, or up to 5 carbon atoms.Examples of heteroaryl groups include, but are not limited to,quinolinyl, isoquinolinyl, quinazolinyl, quinoxalinyl, cinnolinyl,benzofuranyl, benzomercaptophenyl, benzoxazolyl, benzothiazolyl,benzimidazolyl, indolyl, phthalazinyl, benzothiadiazolyl,benzotriazinyl, phenazinyl, phenanthridinyl, acridinyl,azaphenanthrenyl, and indazolyl.

The Ar¹ group in Formula I, in some embodiments, can be substituted withan electron withdrawing group or an electron withdrawing group incombination with an electron donating group provided that thearylsulfinate salt has an oxidation potential in N,N-dimethylformamideof 0.0 to +0.4 volts versus a silver/silver nitrate reference electrode.Electron donating groups can be selected, for example, from a primaryamino, secondary amino, tertiary amino, hydroxy, alkoxy, aryloxy, alkyl,or combinations thereof. Electron withdrawing groups can be selected,for example, from a halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy,alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo,alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl,azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato,aminocarbonyl, or combinations thereof.

In some embodiments, the Ar¹ group includes an electron withdrawinggroup that is conjugated to the sulfinate group. For example, the Ar¹group can be a phenyl substituted with an electron withdrawing groupselected from halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy,alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo,alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl,azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato,aminocarbonyl, or combinations thereof.

Specific examples of the arylsulfinate anion of Formula I include, butare not limited to, 4-chlorobenzenesulfinate, 4-cyanobenzenesulfinate,4-ethoxycarbonylbenzenesulfinate, 4-trifluoromethylbenzenesulfinate,3-trifluoromethylbenzenesulfinate, 1-naphthalenesulfinate,2-naphthalenesulfinate, and 1-anthraquinonesulfinate.

The arylsulfinate salts have a cation with at least one carbon atom andeither a positively charged nitrogen atom or a positively chargedphosphorus atom. In one embodiment, the cation of the arylsulfinate isof Formula II

where R¹ is an alkyl or aryl and each R⁴ is independently a hydrogen,alkyl, or aryl. The R¹ and R⁴ groups can be unsubstituted orsubstituted. An alkyl group can be substituted with a hydroxy. An arylcan be substituted with an alkyl, hydroxy, or combinations thereof.

In some examples of Formula II, R¹ and each R⁴ group are independently aC₂₋₃₀ alkyl that is unsubstituted or substituted with a hydroxy. Forexample, R¹ and each R⁴ independently can be an alkyl group having up to20, up to 10, up to 8, up to 6, or up to 4 carbon atoms. The alkyl groupoften has at least 2, at least 3, at least 4, at least 6, or at least 8carbon atoms. The alkyl group can have 4 to 30, 8 to 30, 3 to 10, 4 to10, 4 to 8, or 4 to 6 carbon atoms in some compounds. In a specificexample, the cation of the arylsulfinate salt is a tetrabutylammoniumion.

In other examples of Formula II, R¹ and two R⁴ groups are eachindependently a C₂₋₃₀ alkyl that can be unsubstituted or substitutedwith a hydroxy. The remaining R⁴ group is hydrogen. In still otherexamples, R¹ and one R⁴ group are each independently a C₄₋₃₀ alkyl thatis unsubstituted or substituted with a hydroxy; and the two remaining R⁴groups are hydrogen. In yet other examples, R¹ is a C₈₋₃₀ alkyl that isunsubstituted or substituted with a hydroxy; and the R⁴ groups arehydrogen.

The R¹ group and each of the R⁴ groups in Formula II independently canbe an aryl group that is unsubstituted or substituted with an alkyl,hydroxy, or combinations thereof. An exemplary cation istetraphenylammonium ion. In another example, R¹ and one R⁴ areindependently an aryl group that is unsubstituted or substituted with analkyl, hydroxy, or combinations thereof; and the two remaining R⁴ groupsare hydrogen. An exemplary cation is diphenylammonium ion.

In other embodiments, the cation of the arylsulfinate salt is a ringstructure that includes a 4 to 12 member heterocyclic group with apositively charged nitrogen atom. The heterocyclic group can besaturated or unsaturated and can contain up to three heteroatomsselected from nitrogen, oxygen, sulfur, or combinations thereof (i.e.,there is one positively charged nitrogen atom and up to two otherheteroatoms selected from nitrogen, oxygen, sulfur, or combinationsthereof). The ring structure can be unsubstituted or have a substituentselected from an alkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto,amino, hydroxy, azo, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl,halocarbonyl, or combinations thereof.

The heterocyclic group in the cationic ring structure can be a singlering, bicyclic, or can be fused to another cyclic or bicyclic group. Thefused cyclic or bicyclic group can be saturated or unsaturated and canhave 0 to 3 heteroatoms. The ring structure can include up to 30 carbonatoms, up to 24 carbon atoms, up to 18 carbon atoms, up to 12 carbonatoms, up to 6 carbon atoms, or up to 4 carbon atoms and up to 6heteroatoms, up to 4 heteroatoms, up to 2 heteroatoms, or 1 heteroatom.In some embodiments, the ring structure is a 4 to 12 member heterocyclicgroup that is a fused to an aromatic ring having 0 to 3 heteroatoms.

Suitable examples of five member heterocyclic groups that contain apositively charged nitrogen atom include, but are not limited to, apyrrolium ion, pyrazolium ion, pyrrolidinium ion, imidazolium ion,triazolium ion, isoxazolium ion, oxazolium ion, thiazolium ion,isothiazolium ion, oxadiazolium ion, oxatriazolium ion, dioxazolium ion,and oxathiazolium ion. These ions can be unsubstituted or substitutedwith an alkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto, amino,hydroxy, azo, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl,halocarbonyl group, or combinations thereof. In some applications, thecation is an imidazolium ion or oxazolium ion that is unsubstituted orsubstituted.

The five member heterocyclic groups can be fused to another cyclicgroup. In some exemplary ring structures, a five membered heterocyclicgroup is fused to an aromatic group. Exemplary ring structures include,but are not limited to, an indole ion, indazolium ion,benzopyrrolidinium ion, benzimidazolium ion, benzotriazolium ion,benzisoxazolium ion, benzoxazolium ion, benzothiazolium ion,benzisothiazolium ion, benzoxadiazolium ion, benzoxatriazolium ion,benzodioxazolium ion, benzoxathiazolium ion, carbozolium ion, andpurinium ion. These ions can be unsubstituted or substituted with analkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto, amino, hydroxy, azo,cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl group, orcombinations thereof. In some applications, the cation is abenzoxazolium ion or a benzothiazolium ion that is unsubstituted orsubstituted.

Suitable examples of six member heterocyclic groups that contain apositively charged nitrogen atom include, but are not limited to, apyridinium ion, pyridazinium ion, pyrimidinium ion, pyrazinium ion,piperazinium ion, triazinium ion, oxazinium ion, piperidinium ion,oxathiazinium ion, oxadiazinium ion, and morpholinium ion. These ionscan be unsubstituted or substituted with an alkyl, aryl, acyl, alkoxy,aryloxy, halo, mercapto, amino, hydroxy, azo, cyano, or carboxy,alkoxycarbonyl, aryloxycarbonyl, halocarbonyl group, or combinationsthereof. In some applications, the cation is a pyridinium ion or amorpholinium ion that is unsubstituted or substituted.

The six member heterocyclic groups can be fused to another cyclic group.In some exemplary ring structures, a six membered heterocyclic group isfused to an aromatic group. Exemplary ring structures include, but arenot limited to, isoquinolinium ion, quinolinium ion, cinnolinium ion,quinazolinium ion, benzopyrazinium ion, benzopiperazinium ion,benzotriazinium ion, benzoxazinium ion, benzopiperidinium ion,benzoxathiazinium ion, benzoxadizinium ion, benzomorpholinium ion,naphtyridinium ion, and acridinium ion. These ions can be unsubstitutedor substituted with an alkyl, aryl, acyl, alkoxy, aryloxy, halo,mercapto, amino, hydroxy, azo, cyano, or carboxy, alkoxycarbonyl,aryloxycarbonyl, halocarbonyl group, or combinations thereof.

Suitable examples of seven member heterocyclic groups that contain apositively charged nitrogen atom include, for example, an azepinium ionand diazepinium ion. These ions can be unsubstituted or substituted withan alkyl, aryl, acyl, alkoxy, aryloxy, halo, mercapto, amino, hydroxy,azo, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonylgroup, or combinations thereof.

Examples of heterocyclic groups that are bicyclic include, but are notlimited to, N-alkylated or N-protonated 1,4-diazabicyclo [2.2.2] octaneand N-alkylated or N-protonated 1-azabicyclic [2.2.2] octane that isunsubstituted or substituted with an alkyl, aryl, acyl, alkoxy, aryloxy,halo, mercapto, amino, hydroxy, azo, cyano, carboxy, alkoxycarbonyl,aryloxycarbonyl, halocarbonyl group, or combinations thereof.

In other embodiments, the cation of the arylsulfinate salt contains apositively charged phosphorus atom of Formula III

where each R² is independently an alkyl or aryl that is unsubstituted orsubstituted. An alkyl group can be substituted with a hydroxy. An arylcan be substituted with an alkyl, hydroxy, or combinations thereof.

In some examples of Formula III, all of the R² groups are an aryl group.For example, the cation can be a tetraphenylphosphonium ion. In otherexamples, one, two, or three of the R² groups are an aryl with theremaining R² group or groups being a C₂₋₃₀ alkyl.

Some of the arylsulfinate salts can have an anion of Formula IV

and a cation that contains a positively charged nitrogen atom. InFormula IV, R³ can be in an ortho, para, or meta position of the benzenering and is an electron withdrawing group selected from halo, cyano,fluoroalkyl, perfluoroalkyl, carboxy, alkoxycarbonyl, aryloxycarbonyl,halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl,perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl,dialkylphosphonato, diarylphosphonato, or aminocarbonyl. In somecompounds, R³ is selected from cyano, carboxy, alkoxycarbonyl,aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl,aryloxysulfonyl, perfluoroalkylsulfonyl, or alkylsulfonyl. In othercompounds, R³ is a halo, cyano, or alkoxycarbonyl group.

Specific examples Formula IV where R³ is located in the para position ofthe phenyl ring include 4-cyanobenzenesulfinate,4-chlorobenzenesulfinate, 4-ethoxycarbonylbenzenesulfinate, and4-trifluoromethylbenzenesulfinate. A specific example of R³ located inthe meta position of the phenyl ring includes3-trifluoromethylbenzenesulfinate.

For some applications, the arylsulfinate salt includes an anion ofFormula IV and a cation that is a tetraalkyammonium ion. The alkylgroups of the tetraalkylammonium ion can be the same or different andtypically contain 2 to 30 carbon atoms. For example, the alkyl groupscan contain 4 to 30 carbon atoms, 8 to 30 carbon atoms, 3 to 10 carbonatoms, 4 to 10 carbon atoms, 4 to 8 carbon atoms, or 4 to 6 carbonatoms. Specific arylsulfinate salts include, but are not limited to,tetrabutylammonium 4-chlorobenzenesulfinate, tetrabutylammonium4-cyanobenzenesulfinate, tetrabutylammonium4-ethoxycarbonylbenzenesulfinate, tetrabutylammonium4-trifluoromethylbenzenesulfinate, and tetrabutylammonium3-trifluoromethylbenzenesulfinate.

Other specific examples of electron donors include, but are not limitedto, tetrabutylammonium 1-naphthalenesulfinate, tetrabutylammonium2-naphthalenesulfinate, and tetrabutylammonium 1-anthraquinonesulfinate,1-ethyl-3-methylimidazolium 4-cyanobenzenesulfinate,N,N-dimethylmorpholinium 4-cyanobenzenesulfinate,3-ethyl-2-methylbenxoxazolium 4-cyanobenzenesulfinate,1-methyl-4-aza-1-azoniabicyclo[2.2.2]octane 4-cyanobenzenesulfinate, andN-hexadecylpyridinium 4-cyanobenzenesulfinate.

In some embodiments, the arylsulfinates can be stored as a neat compoundat room temperature without undergoing oxidative degradation. Forexample, some of the arylsulfinates can be stored for greater than oneday, greater than 2 days, greater than 1 week, greater than 2 weeks, orgreater than 1 month. The time required at room temperature (i.e., 20°C. to 25° C.) to oxidize 50 percent of the compound (t_(1/2)) can beused to compare the relative ease of oxidative degradation of variousarylsulfinates. The t_(1/2) is calculated based on pseudo-first orderkinetics as described in K. A. Connors, Chemical Kinetics: The Study ofReaction Rates in Solution, Chapter 2, VCH, New York, 1990.

The arylsulfinate salt has an oxidation potential inN,N-dimethylformamide of +0.4 to 0.0 volts versus a silver/silvernitrate reference electrode. In some embodiments, the electron donor hasan oxidation potential in N,N-dimethylformamide of +0.08 to 0.3 volts or+0.08 to +0.2 volts versus a silver/silver nitrate reference electrode.

Another component of the compositions is an electron acceptor having areduction potential in N,N-dimethylformamide of +0.4 to −1.0 voltsversus a silver/silver nitrate reference electrode. In some embodiments,the electron acceptor has a reduction potential in N,N-dimethylformamideof +0.1 to −1.0 volts, 0.0 to −1.0 volts, −0.1 to −1.0 volts, or −0.5 to−1.0 volts versus a silver/silver nitrate reference electrode.

Suitable electron acceptors include, but are not limited to, metal ionsin an oxidized state, persulfates, peroxides, iodonium salts,hexaarylbisimidazoles, or combinations thereof. In some applications,the electron acceptor is selected to be soluble in monomers capable ofundergoing free radical polymerization reactions.

The electron acceptor is usually not mixed with the electron donor priorto use in an initiator system if the electron acceptor is a metal ion inan oxidized state, a peroxide, a persulfate, or combinations thereof.These electron acceptors can often react with the electron donor at roomtemperature (i.e., 20° C. to 25° C.) or at an elevated temperature(e.g., up to 150° C.) within a relatively short period of time (e.g.,less than 1 hour, less than 30 minutes, less than 10 minutes, or lessthan 5 minutes). Initiator systems containing metal ions in an oxidizedstate, peroxides, or persulfates typically do not require a sensitizingcompound to activate the initiator system. Such initiator systems can beinitiated without activation by actinic radiation (i.e., the initiatorsystems are thermal systems).

Suitable electron acceptor metal ions include, for example, ions ofgroup III metals, transition metals, and lanthanide metals. Specificmetal ions include, but are not limited to, Fe(III), Co(III), Ag(I),Ag(II), Cu(II), Ce(III), Al (III), Mo(VI), and Zn(II). Suitable electronacceptor peroxides include benzoyl peroxide, lauryl peroxide, and thelike. Suitable electron acceptor persulfates include, for example,ammonium persulfate, tetraalkylammonium persulfate (e.g.,tetrabutylammonium persulfate), and the like.

In some embodiments, the electron acceptor does not include metal ionsin an oxidized state, peroxides, or persulfates. For example, if theinitiator system is used in a photopolymerization method (i.e., theinitiator is a photoinitiator system), the electron acceptor typicallyis selected so that it does not react directly with the electron donorat room temperature. The electron acceptor and the electron donortypically can be stored together for at least one day prior toactivation of the photoinitiator system by excitation of a sensitizingcompound. Electron acceptors suitable for photopolymerization reactionsinclude, but are not limited to, iodonium salts, hexaarylbisimidazoles,or combinations thereof. In some photoinitiator systems,hydroxy-containing materials are added to enhance the storage stability.

In some applications, particularly applications that use aphotoinitiator system, the electron donor has a reduction potential inN,N-dimethylformamide of +0.1 to −1.0 volts, 0.0 to −1.0 volts, −0.1 to−1.0 volts, or −0.5 to −1.0 volts versus a silver/silver nitratereference electrode. Electron acceptors having such reduction potentialsinclude iodonium salts. The iodonium salts are often diaryliodoniumsalts. Diaryliodonium salts can be combined with an arylsulfinate saltand polymerizable material to form a stable composition.

Suitable iodonium salts are described in further detail in U.S. Pat.Nos. 3,729,313; 3,741,769; 3,808,006; 4,250,053; 4,394,403; 5,545,676;and 5,998,495, the iodonium salt disclosures of which are incorporatedherein by reference. The iodonium salt can be a simple salt, a metalcomplex salt, or combinations thereof. Examples of simple salts includethose having an anion such as a halide, sulfonate, carboxylate, orcombinations thereof. Examples of metal complex salts include thosehaving an anion such as hexafluorophosphate, hexafluoroarsenate,hexafluoroantimonate, pentafluorohydroxyantimonate, tetrafluoroborate,tetra(pentafluorophenyl)borate, or combinations thereof.

The iodonium metal complex salts can be prepared by metathesis ofcorresponding iodonium simple salts (such as, for example,diphenyliodonium chloride or diphenyliodonium bisulfite) in accordancewith the teachings of Beringer et al., J. Am. Chem. Soc., 81, 342(1959). In a specific example, the metal complex salt diphenyliodoniumtetrafluoroborate can be prepared by the addition of an aqueous solutioncontaining silver fluoroborate, fluoroboric acid, and phosphorous acidto an aqueous solution of diphenyliodonium chloride. The silver halidethat precipitates can be filtered off and the filtrate concentrated toyield diphenyliodonium tetrafluoroborate that may be purified byrecrystallization.

The diaryliodonium simple salts can be prepared in accordance withBeringer et al., above, by various methods including coupling of twoaromatic compounds with iodyl sulfate in sulfuric acid; coupling of twoaromatic compounds with an iodate in acetic acid-acetic anhydride;coupling of two aromatic compounds with an iodine acrylate in thepresence of an acid; or condensation of an iodoso compound (e.g., iodosodiacetate) or an iodoxy compound with another aromatic compound in thepresence of an acid.

Exemplary diaryliodonium salts include diphenyliodonium chloride,diphenyliodonium tetrafluoroborate, di(4-methylphenyl)iodoniumtetrafluoroborate, phenyl-4-methylphenyliodonium tetrafluoroborate,di(4-heptylphenyl)iodonium tetrafluoroborate,phenyl-4-heptylphenyliodonium tetrafluoroborate,di(3-nitrophenyl)iodonium hexafluorophosphate,di(4-chlorophenyl)iodonium hexafluorophosphate, di(naphthyl)iodoniumtetrafluoroborate, di(4-trifluoromethylphenyl)iodoniumtetrafluoroborate, diphenyliodonium hexafluorophosphate,di(4-methylphenyl)iodonium hexafluorophosphate, diphenyliodoniumhexafluoroarsenate, di(4-phenoxyphenyl)iodonium tetrafluoroborate,phenyl-2-thienyliodonium hexafluorophosphate,3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate,diphenyliodonium hexafluoroantimonate, 2,2′-diphenyliodoniumtetrafluoroborate, di(2,4-dichlorophenyl)iodonium hexafluorophosphate,di(4-bromophenyl)iodonium hexafluorophosphate,di(4-methoxyphenyl)iodonium hexafluorophosphate,di(3-carboxyphenyl)iodonium hexafluorophosphate,di(3-methodycarbonylphenyl)iodonium hexafluorophosphate,di(3-methoxysulfonylphenyl)iodonium hexafluorophosphate,di(4-acetamidophenyl)iodonium hexafluorophosphate,di(2-benzothienyl)iodonium hexafluorophosphate, diphenyliodoniumhexafluoroantimonate, and diphenyliodoniumtetra(pentafluorophenyl)borate.

In some applications, the electron acceptor is diphenyliodoniumchloride, diphenyliodonium hexafluorophosphate, diphenyliodoniumtetrafluoroborate, diphenyliodonium hexafluoroantimonate,diphenyliodonium tetra(pentafluorophenyl)borate, or combinationsthereof. These electron acceptors tend to promote faster reactions andto be more soluble in inert organic solvents compared to some otheriodonium salts.

The initiator system can include a hexaarylbisimidazole compound as theelectron acceptor. Such compounds can be synthesized as described in J.Org. Chem., 36, 2762 (1971). A hexaarylbisimidazole is commerciallyavailable under the trade designation SPEEDCURE BCIM from Lambson, WestYorkshire, England.

For compositions that are a photoinitiator system, a solution that iscolorless to the eye is often formed when the electron acceptor isdissolved in a suitable solvent such as an alcohol or in anethylenically unsaturated monomer. A solution of the electron acceptorin an alcohol typically does not absorb in the visible region of theelectromagnetic spectra. That is, the molar extinction coefficient ofthe electron acceptor can be less than 100 or less than 50 l-mole⁻¹ cm⁻¹at 350 nm.

The oxidation potential of the electron donor can be greater than, equalto, or less than the reduction potential of the electron acceptor. Insome embodiments, the oxidation potential of the arylsulfinate salt ismore positive than the reduction potential of the electron acceptor.Such compositions tend to have low reactivity in the presence of amonomer capable of undergoing a free radical polymerization reaction atroom temperature or in the absence of actinic radiation. In otherembodiments, the reduction potential of the electron acceptor is morepositive than the oxidation potential of the arylsulfinate salt. Suchcompositions tend to be reactive upon mixing in the presence of amonomer capable of undergoing a free radical polymerization reaction.The reactivity also can be influenced by other factors such asconcentration of the arylsulfinate salt and the electron acceptor,temperature, and the nature of the other components in the curablecomposition (e.g., the presence of hydroxy-containing compounds candecrease the reactivity of the composition).

The composition can further include a sensitizing compound. The additionof a sensitizing compound allows the composition to be used as aninitiator system for photopolymerization methods. Actinic radiation canbe used to form an excited sensitizing compound. The electron donor candonate an electron to the excited sensitizing compound to form a reducedsensitizing compound that is a radical anion. This radical anion candonate an electron to an electron acceptor to yield an initiating freeradical. The sensitizing compound can be a dye, pigment, or combinationsthereof.

Suitable sensitizing compounds that are dyes include, but are notlimited to, ketones (e.g., monoketones and diketones), coumarin dyes(e.g., ketocoumarins such as Coumarin 153), xanthene dyes (e.g., RoseBengal and Rhodamine 6G), acridine dyes, thiazole dyes, thiazine dyes(e.g., Methylene Blue and Methylene Violet), oxazine dyes (e.g., BasicBlue 3 and Nile Blue Chloride), azine dyes (e.g., Methyl Orange),aminoketone dyes, porphyrins (e.g., porphyrazine), aromatic polycyclichydrocarbons, p-substituted aminostyryl ketone compounds, aminotriarylmethanes, cyanine dyes (e.g., the cyanine dye described in Biochemistry,12, 3315 (1974)), squarylium dyes, pyridinium dyes, benzopyrilium dyes,and triarylmethane (e.g., Malachite Green). In some applications, thesensitizing compounds include xanthenes, monoketones, diketones, orcombinations thereof. Other suitable sensitizing dyes are described inF. J., Green, The Sigma-Aldrich Handbook of Stains, Dyes, andIndicators, Aldrich Chemical Company, Inc., Milwaukee, Wis. (1990).

In some embodiments, the sensitizing compound is a xanthene dye such asfluorosceins, rhodamines, eosins, and pyronins.

Exemplary monoketones include 2,2-dihydroxybenzophenone,4,4-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, di-2-pyridylketone, di-2-furanyl ketone, di-2-mercaptophenyl ketone, benzoin,fluorenone, chalcone, Michler's ketone, 2-fluoro-9-fluorenone,2-chloromercaptoxanthone, acetophenone, benzophenone, 1- or2-acetonaphthone, 9-acetylanthracene, 2-, 3-, or 9-acetylphenanthrene,4-acetylbiphyenyl, propiophenone, n-butyrophenone, valerophenone, 2-,3-, or 4-acetylpyridine, 3-acetylcoumarin, and the like.

Exemplary diketones include aralkyldiketones such as anthraquinone,phenanthrenequinone, o-, m-, and p-diacetylbenzene, 1,3-, 1,4-, 1,5-,1,6-, 1,7-, and 1-8 diacetylnaphthalene, 1,5-, 1,8-, and9,10-diacetylanthracene, and the like. Exemplary alpha-diketones include2,3-butanedione, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione,2,3-heptanedione, 3,4-heptanedione, 2,3-octanedione, 4,5-octanedione,benzil, 2,2′-, 3,3′-, and 4,4′-dihydroxybenzil, furil,di-3,3′-indolylethanedione, 2,3-bornanedione (camphorquinone), biacetyl,1,2-cyclohexanedione, 1,2-naphthaquinone, acenaphthaquinone, and thelike.

The dye can have a molar extinction coefficient up to about 150,000l-mole⁻¹ cm⁻¹. In some applications, the dye has a molar extinctioncoefficient that is up to 85,000 l-mole⁻¹ cm⁻¹, up to 70,000, up to50,000, up to 30,000, up to 10,000, or up to 5,000 l-mole⁻¹ cm⁻¹.

For applications requiring deep cure (e.g., cure of highly filledcomposites such as dental composites or cure of a thick sample), asensitizing compound is typically selected that has an extinctioncoefficient less than 1000 l-mole⁻¹ cm⁻¹. In some examples, theextinction coefficient at the wavelengths of actinic radiation used forphotopolymerization is less than 500 or less than 100 l-mole⁻¹ cm⁻¹. Thealpha-diketones, for example, are sensitizing compounds that can be usedfor such applications.

The sensitizing compound also can be a pigment as described in U.S. Pat.Nos. 4,959,297 and 4,257,915, the disclosures of which are incorporateherein by reference in their entirety. Suitable inorganic pigmentsinclude, but are not limited to, titanium dioxide, strontium titanate,barium titanate, zinc oxide, zinc sulfide, zinc selenide, cadmiumsulfide, cadmium selenide, cadmium telluride, or combinations thereof.Suitable organic pigments include, but are not limited to,phthalocyanine blue (pigment blue 15), copper polychlorophthalocyaninegreen (pigment green 7), copper polybromochlorophthalocyanine (pigmentgreen 36), perylene scarlet (vat red 29), perylene vermillion (pigmentred 23), perylene maroon, perylene Bordeaux, perylene dianhydride(perylene red), and those described in “Pigments-Inorganic” and“Pigments-Organic” in Kirk-Othmer Encyclopedia of Chemical Technology,Third ed., Volume 17, pp. 788-817, John Wiley and Sons, New York, 1982.The organic pigments also can be semiconducting polymers as described byY. M. Paushkin et al., Organic Polymeric Semiconductors, John Wiley &Sons, New York, 1974 and by J. M. Pearson, Pure and Appl. Chem., 49,463-477 (1977).

The composition can further include monomers that can be polymerizedusing a free-radical polymerization reaction. The monomers typicallycontain at least one ethylenically-unsaturated double bond. Themonomers, for example, can be monoacrylates, diacrylates, polyacrylates,monomethacrylates, dimethacrylates, polymethacrylates, or combinationsthereof. The monomers can be unsubstituted or substituted with ahydroxy. Exemplary monomers include methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate,isopropyl methacrylate, n-hexyl acrylate, stearyl acrylate, allylacrylate, glycerol acrylate, glycerol diacrylate, glycerol triacrylate,ethyleneglycol diacrylate, diethyleneglycol diacrylate,triethyleneglycol diacrylate, 1,3-propanediol diacrylate,1,3-propanediol dimethacrylate, trimethylolpropane triacrylate,1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate,pentaerythritol triacrylate, pentaerythritol tetraacrylate,pentaerythritol tetramethacrylate, sorbitol hexaacrylate,bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, andtris-hydroxyethyl-isocyanurate trimethylacrylate. The monomers also canbe bis-acrylates and bis-methacrylates of polyethylene glycol having anaverage molecular weight (M_(n)) of 200 to 500; copolymerizable mixturesof acrylated monomers such as those described in U.S. Pat. No.4,652,274, incorporated herein by reference in its entirety; acrylatedmonomers such as those described in U.S. Pat. No. 4,642,126,incorporated herein by reference in its entirety; unsaturated amidessuch as methylene bis-arylamide, methylene bis-methacrylamide,1,6-hexamethylene bis-acrylamide, diethylene triamine tris-acrylamide,and beta-methacrylaminoethyl methacrylate; and vinyl monomers such asstyrene, diallyl phthalate, divinyl succinate, divinyl adipate, anddivinylphthalate. Mixtures of two or more monomers can be used, ifdesired.

Some compositions, such as those that undergo photopolymerizationreactions, can include a hydroxy-containing material. Thehydroxy-containing material can improve the storage stability of somecompositions. Hydroxy-containing material, for example, can be analcohol, a hydroxy-containing monomer, or combinations thereof.

Suitable alcohols include, but are not limited to, methanol, ethanol,1-propanol, 2-propanol, 2-methyl-2-propanol, 1-butanol, 2-butanol,1-pentanol, neopentyl alcohol, 3-pentanol, 1-hexanol, 1-heptanol,1-octanol, 2-phenoxyethanol, cyclopentanol, cyclohexanol,cyclohexylmethanol, 3-cyclohexyl-1-propanol, 2-norbornanemethanol, andtetrahydrofurfuryl alcohol.

The alcohol can be a diol or a polyol. Suitable diols include materialsranging in size from ethylene glycol to a polyethylene glycol. Exemplarydiols and polyols include, but are not limited to, 1,2-ethanediol,1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol,2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol,2-ethyl-1,6-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol,neopentyl glycol, glycerol, trimethylolpropane, 1,2,6-hexanetriol,trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol,diethylene glycol, triethylene glycol, tetraethylene glycol, glycerine,2-ethyl-2-(hydroxymethyl)-1,3-propanediol, 2-ethyl-1,3-pentanediol,1,4-cyclohexanedimethanol, and 1,4-benzene-dimethanol. Other usefulpolyols are disclosed in U.S. Pat. No. 4,503,211, the disclosure ofwhich is incorporated herein by reference.

Higher molecular weight polyols include the polyethylene oxide andpolypropylene oxide polymers in the molecular weight (M_(n)) range of200 to 20,000 such as polyethyleneoxide materials available from DowChemical Co., Midland, Mich. under the trade designation CARBOWAX;carpolactone polyols in the molecular weight (M_(n)) range of 200 to5,000 such as polyol materials available from Dow Chemical Co., Midland,Mich. under the trade designation TONE; polytetramethylene ether glycolin the molecular weight (M_(n)) range of 200 to 4,000 such as thematerials available from DuPont, Wilmington, Del. under the tradedesignation TERATHANE and from BASF, Mount Olive, N.J. under the tradedesignation POLYTHF 250; polyethylene glycol such as material availablefrom Dow Chemical Co., Midland, Mich. under the trade designation PEG200; hydroxy-terminated polybutadiene resins such as materials fromAtofina, Philadelphia, Pa. under the trade designation POLYBD; phenoxyresins such as those commercially available from Phenoxy Associates,Rock Hill, S.C.; and similar materials supplied by other manufacturers.

Suitable hydroxy-containing monomers include hydroxy substituted estersof acrylic acid or hydroxy substituted esters of methacrylic acid.Exemplary hydroxy-containing monomers include 2-hydroxyethylacrylate,2-hydroxyethylmethacrylate, 4-hydroxybutylactylate,4-hydroxybutylmethacrylate, glycerol acrylate, glycerol diacrylate,glycerol methacrylate, glycerol dimethacrylate, and the like. In someapplications, all of the monomers are hydroxy-containing materials.

The components of the initiator system can be present in an amounteffective to enable free radical polymerization of theethylenically-unsaturated monomers. The amount of the electron donor andthe electron acceptor can affect the kinetics of the polymerizationreaction and the shelf life of the composition. The rate of the reactiontypically increases with an increased concentration of the electronacceptor and electron donor. The shelf life typically shortens withhigher levels of the electron donor and electron acceptor.

In some applications, the electron donor and the electron acceptor caneach be present in an amount up to 4 weight percent based on the weightof the monomer. The amount of the electron donor and the electronacceptor can be the same or different. In some embodiments, the electrondonor and the electron acceptor are each present in an amount up to 3weight percent, up to 2 weight percent, up to 1 weight percent, or up to0.5 weight percent based on the weight of the monomers. For example, theelectron donor and the electron acceptor can each be present in anamount of 0.1 to 4 weight percent, 0.1 to 3 weight percent, 0.1 to 2weight percent, or 0.5 to 1 weight percent based on the weight of themonomers.

The sensitizing compound, if present, is often used in an amount up to 4weight percent based on the weight of the monomer. In some applications,the sensitizing compound is present in an amount up to 3 weight percent,up to 2 weight percent, up to 1 weight percent, or up to 0.5 weightpercent based on the weight of the monomers. For example, thesensitizing compound can be present in an amount of 5 ppm to 4 weightpercent, 10 ppm to 2 weight percent, 15 ppm to 1 weight percent, or 20ppm to 0.5 weight percent based on the weight of the monomers.

The compositions can contain a wide variety of additives depending onthe desired use of the polymerized material. Suitable additives includesolvents, diluents, resins, binders, plasticizers, inorganic and organicreinforcing or extending fillers, thixotropic agents, UV absorbers,medicaments, and the like.

In some embodiments, the components of the compositions can be selectedto provide a useful combination of cure speed, cure depth, and shelflife. Some compositions can cure well even when loaded with largeamounts of fillers. The compositions can be used to form foams, shapedarticles, adhesives, filled or reinforced composites, abrasives,caulking and sealing formulations, casting and molding formulations,potting and encapsulating formulations, impregnating and coatingformulations, and the like.

Suitable applications for the compositions include, but are not limitedto, graphic arts imaging (e.g., for color proofing systems, curableinks, and silverless imaging), printing plates (e.g., for projectionplates and laser plates), photoresists, solder masks for printed circuitboards, coated abrasives, magnetic media, photocurable adhesives (e.g.,for orthodontics and general bonding applications), and photocurablecomposites (e.g., for autobody repair and dental restoratives),protective coatings, and abrasion resistant coatings. The compositionsare also suitable for use in a multi-photon process, where highintensity/short pulse lasers are used in combination with suitable dyesand co-reactants to produce polymerizable compositions that are usefulfor imaging, microreplication, and stereolithographic applications. Thecompositions can be used in other applications that are known to thoseskilled in the art.

Polymerization Methods

The invention also provides methods for polymerizing ethylenicallyunsaturated monomers using free radical polymerization reactions. Themethods can be photopolymerization methods, thermal polymerizationmethods, or combinations thereof.

The photopolymerization method includes irradiating a photopolymerizablecomposition with actinic radiation until the photopolymerizablecomposition gels or hardens. The photopolymerizable composition includesa photoinitiator system and monomers capable of undergoing free radicalpolymerization reactions (i.e., ethylenically unsaturated monomers).Three components are typically used in the photoinitiator system: anelectron donor, an electron acceptor, and a sensitizing compound. Insome embodiments of the photopolymerization method, thephotopolymerizable composition can be mixed together and stored for atleast one day prior to use.

The electron donor in the photoinitiator system has an oxidationpotential in N,N-dimethylformamide of 0.0 to +0.4 volts versus asilver/silver nitrate reference electrode and includes an arylsulfinatesalt having an anion of Formula IAr¹—SO₂ ⁻  Iand a cation that contains at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom. The Ar¹ group in Formula I is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl. A substituted Ar¹ group can have asubstituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group.

The electron acceptor in N,N-dimethylformamide usually has a reductionpotential in the range of +0.4 to −1.0 volts versus a silver/silvernitrate reference electrode. In some embodiments, the electron acceptorhas a reduction potential in N,N-dimethylformamide of +0.1 to −1.0volts, 0.0 to −1.0 volts, −0.1 to −1.0 volts, or −0.5 to −1.0 voltsversus a silver/silver nitrate reference electrode. Suitable electronacceptors for photopolymerization methods are often selected to notreact directly with the arylsulfinate electron donors, at least at roomtemperature. A solution of the electron acceptor dissolved in a suitablesolvent such as an alcohol or dissolved in an ethylenically unsaturatedmonomer is typically colorless to the eye. Exemplary electron acceptorsinclude hexaarylbisimidazoles and diaryliodonium salts.

The photopolymerizable compositions can include a wide variety ofdifferent types of sensitizing compounds such as dyes, organic pigments,inorganic pigments, or combinations thereof. In some embodiments, thesensitizing compound can change colors indicating that the polymericmaterial has been cured. The color changes can be attributed to chemicalalterations to the sensitizing compound.

The photoinitiator system can be activated by exposing the sensitizingcompound to actinic radiation having a wavelength in the range of 250 to1000 nanometers. In some applications, the actinic radiation has awavelength in the range of 300 to 1000 nanometers, in the range of 350to 1000 nanometers, in the range of 250 to 850 nanometers, in the rangeof 250 to 800 nanometers, in the range of 400 to 800 nanometers, in therange of 425 to 800 nanometers, or in the range of 450 to 800nanometers. The electron donor can donate electrons to the excitedsensitizing compound. The sensitizing compound can be reduced and theelectron donor can be oxidized. The reduced sensitizing compound is aradical anion that can donate an electron to an electron acceptor toyield an initiating free radical for the polymerization reaction. Thatis, the initiating free radical is the reduced electron acceptor. Insome instances, the oxidized electron donor is a radical species thatalso can function as an initiating free radical for the polymerizationreaction.

Monomers suitable for photopolymerization methods typically include anethylenically unsaturated monomer such as a monoacrylate,monomethacrylate, diacrylate, dimethacrylate, polyacrylate,polymethacrylate, or combinations thereof. In some applications, atleast some of the monomers are hydroxy-containing monomers such ashydroxy substituted esters of acrylic acid or hydroxy substituted estersof methacrylic acid.

The photopolymerizable composition with a photoinitiator systemtypically includes a hydroxy-containing material. Suitablehydroxy-containing materials include, for example, alcohols,hydroxy-containing monomers, or combinations thereof. The amount ofhydroxy-containing material can alter the amount of time that thepolymerizing composition can be stored prior to use. The storagestability often increases with an increase in the amount ofhydroxy-containing material in the photopolymerizable composition. Insome applications, the photopolymerizable composition includes no lessthan 5 weight percent, no less than 10 weight percent, no less than 20weight percent, no less than 30 weight percent, or no less than 40weight percent hydroxy-containing materials based on the weight of thephotopolymerizable composition.

In some embodiments, visible light can be used to excite the sensitizingcompound and activate the photopolymerizable composition. This can beadvantageous because relatively inexpensive light sources can be used.Light sources emitting in the visible region of the electromagneticspectrum tend to be less expensive than those emitting, for example, inthe ultraviolet region. Other light sources that include ultravioletradiation or a combination of ultraviolet and visible radiation also canbe used. Typical light sources include, but are not limited to, mercuryvapor discharge lamps, carbon arcs, tungsten lamps, xenon lamps,sunlight, lasers, light emitting diodes, and the like.

The invention also provides a method of polymerization that includesforming a polymerizable composition and reacting the polymerizablecomposition. The polymerizable composition includes an ethylenicallyunsaturated monomer, an electron donor having an oxidation potential inN,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silvernitrate reference electrode, and an electron acceptor having a reductionpotential in N,N-dimethylformamide of +0.4 to −1.0 volts versus asilver/silver nitrate reference electrode. The electron donor includesan arylsulfinate salt having an anion of Formula IAr¹—SO₂ ⁻  Iand having a cation that contains at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom. The Ar¹ group in Formula I is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl. A substituted Ar¹ group can have asubstituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group.

In thermally initiated free radical polymerization reactions, theelectron acceptor is often selected to react directly with the electrondonor resulting in the formation of a reduced electron acceptor. Thereduced electron acceptor can be a radical that functions as aninitiating free radical for the polymerization reaction. The reactionbetween the electron donor and acceptor can occur at room temperature(i.e., 20° C. to 25° C.) or at elevated temperatures (e.g., temperaturesup to 150° C.). The electron acceptor and the electron donor aretypically kept in separate containers (i.e., not mixed together) untilpolymerization is desired.

Suitable electron acceptors include metal ions in an oxidized state,peroxides, and persulfates. No sensitizing compound is typically neededto activate the initiator system. However, a sensitizing compound can beadded, if desired, to accelerate the reactivity in the presence ofactinic radiation.

Any ethylenically unsaturated monomer can be used. The monomer istypically a monoacrylate, monomethacrylate, diacrylate, dimethacrylate,polyacrylate, polymethacrylate, or combinations thereof. The monomerscan be unsubstituted or substituted with hydroxy groups.

EXAMPLES

Unless otherwise noted, as used herein:

-   -   the solvents and reagents were or can be obtained from Aldrich        Chemical Co., Milwaukee, Wis. or may be synthesized by known        methods;    -   electrochemical instrumentation for cyclic voltammetry was        obtained from Princeton Applied Research, Oak Ridge, Tenn.;    -   N,N-dimethylformamide was obtained from EM Science, Gibbstown,        N.J.;    -   4-(trifluoromethyl)benzenesulfonyl chloride was obtained from        Alfa Aesar, Ward Hill, Mass.;    -   the term “emim” refers to the 1-ethyl-3-methylimidazolium        cation;    -   the term “4-HBA” refers to 4-hydroxybutyl acrylate;    -   the term “HEA” refers to 2-hydroxyethyl acrylate;    -   the term “KL68 Dye” refers to the dye        bis-[4-(diphenylamino)stryl]-1-(2-ethylhexyloxy),4-(methoxy)benzene;    -   the term “Cyanine 1” refers to        3-methyl-2-[5-(3-methyl-2-benzothiazolinylidene)-1,3-pentadienyl]benzothiazolium        iodide and was prepared according to the general method        disclosed in Biochemistry, 13 (42), 3315-3330 (1974);    -   the term “SR339” refers to 2-phenoxyethyl acrylate and was        obtained from Sartomer Co. Inc., Exton, Pa.;    -   the term “SR238” refers to 1,6-hexanediol diacrylate and was        obtained from Sartomer Co. Inc., Exton, Pa.;    -   the term “SR399” refers to pentaerythritol pentaacrylate and was        obtained from Sartomer Co. Inc., Exton, Pa.;    -   the term “SR351” refers to trimethylolpropane triacrylate which        was obtained from Sartomer Co., Inc., Exton, Pa.;    -   the term “IR140” refers to        5,5′-dichloro-11-diphenylamino-3,3′-diethyl-10,12-ethylenethiatricarobocyanine        perchlorate; and    -   the term “IR780 iodide” refers to        2-[2-[2-chloro-3-[(1,3-dihydro-3,3-dimethyl-1-propyl-2H-indol-2-ylidene)ethylidene]-1-cyclohexen-1-yl]ethenyl]-3,3-dimethyl-1-propylindolium        iodide.        Methods        Measurement of Oxidation Potentials

The electrochemical measurements of the exemplary arylsulfinates weremade using an EG&G PARC Model 175 Universal Programmer, interfaced to aPrinceton Applied Research Model 173 potentiostat/galvanostat fittedwith a Princeton Applied Research Model 179 Digital Coulometer and Model178 Electrometer. The signal was digitized using a Model DI-151R5Waveform Recording System (available from DATAQ Instruments, Inc.,Akron, Ohio) and then stored and analyzed on a Dell OptiPlex XM 590 pc.Scans were run at 100 mV/sec scan rate.

The electrochemical measurements were made using a three-electrodeconfiguration: a reference electrode, a working electrode, and a counterelectrode. The reference electrode was a fritted electrode (obtainedfrom Sargent Welch, Buffalo Grove, Ill.) that was filled with 0.01MAgNO₃ in acetonitrile and fitted with a silver wire 1 mm in diameter byapproximately 19 cm in length. The counter electrode was a platinum wire1.0 mm in diameter and approximately 16 cm long (overall length) formedinto a coil having a coil diameter of approximately 10 mm and a coillength of about 7.5 cm. The working electrode was a glassy carbonelectrode, approximately 3.5 mm in diameter (obtained from BAS, Inc.,West Lafayette, Ind.). The glassy carbon electrode was polished usingfirst a 3.0 micron aluminum oxide powder/deionized water slurry, then a0.3 micron alpha alumina powder/deionized water slurry. The polishingpowders were obtained from Buehler LTD, Evanston, Ill.

The cell was a 50 mL four neck round bottom flask. Each electrode wassealed in the flask using the appropriately sized rubber septum. Thefourth inlet was used to introduce an argon purge to remove oxygen andkeep atmospheric moisture out of the cell.

The supporting electrolyte was tetrabutylammonium hexafluorophosphate(TBA PF₆) (obtained from Southwestern Analytical Chemicals, Inc.,Austin, Tex.). The TBA PF₆ was dried overnight in a vacuum oven at80-90° C. before each experiment. The solvent was N,N-dimethylformamide(DMF), and it was used as received without further purification. Thesolvent was transferred to the electrochemical cell via syringe under anargon atmosphere to minimize atmospheric moisture uptake.

Electrochemical measurements were made by first preparing a 0.1 molarsolution of TBA PF₆ in DMF. This solution was added to the cell, whichcontained a small magnetic stir bar, as argon gas was flowing throughthe cell. After the reference and counter electrodes were connected tothe instrumentation, the working electrode was polished as describedabove and was then inserted into the cell. A background scan wasconducted before the exemplary compounds were added to the cell. Then,approximately 10 mg of the compound was added to the cell and, after ithad dissolved, the measurement was made to record the oxidationpotential. The potential was determined at the peak current for theoxidation or reduction reaction on the first scan. In thisconfiguration, the oxidation potential of ferrocene in an identicalelectrolyte solution appeared at +0.1 volts versus the referenceelectrode.

Measurement of Oxidative Stability

The oxidative stability of the exemplary substituted arylsulfinates wasdetermined by proton nuclear magnetic resonance spectroscopy. Spectra ofsolutions of the compounds in acetonitrile-d₃ were obtained at regularintervals. The resonances of the alkyl groups in the cations were usedas an internal standard to assess the oxidation of the anion.

Preparative Example 1 Preparation of 4-Cyanobenzenesulfonyl Chloride

An intimate mixture 4-carboxybenzenesulfonamide (188 g) and PCl₅ (430 g)was made by combining the solids in a resealable plastic bag andmanually kneading and shaking the bag. The mixture was transferred to around bottom flask that was fitted with a magnetic stir bar and a hoseadapter that was connected to a source of nitrogen gas. The flask wasslowly heated to 60° C. in an oil bath and was held at 60° C. for 5hours as the mixture was stirred. The hose adapter was then connected toa water aspirator through a trap that was cooled with dry ice, and thetemperature of the oil bath was increased to 110° C. while the flask wasevacuated and liquid distilled into the trap. When the rate ofdistillation slowed, the hose adapter was again connected to thenitrogen source and the temperature of the oil bath was raised to 155°C. After an additional 13 hours, the hose adapter was again connected toa water aspirator through a trap and more liquid was distilled. Thereaction flask was then allowed to cool to room temperature, duringwhich time the brown product solidified. The crude product was vacuumdistilled, using a Kugelrohr distillation (available from AldrichChemical Co., Milwaukee, Wis.) at a temperature of 150° C. and apressure of 0.07 mmHg, into a collection bulb that was cooled in an icebath. The solid yellow distillate was washed from the collection bulbwith CH₂Cl₂ and that solution was concentrated to dryness with a rotaryevaporator to afford 167.4 g of product.

Preparative Example 2 Preparation of Potassium4-Ethoxycarbonylbenzenesulfonate

A mixture of sodium 4-carboxybenzenesulfonate (75 g) in deionized water(1200 mL) was heated to 60° C. until the solid was dissolved. Thissolution was passed through a column of a strongly acidic ion-exchangeresin (available under the trade designation AMBERLITE IR-120(PLUS) fromRohm and Haas Co., Philadelphia, Pa.) that had been acidified by washingsequentially with deionized water, concentrated aqueous HCl anddeionized water until the pH of the eluate was approximately 5.5. Thecolumn was then charged with the solution of sodium4-carboxybenzenesulfonate and was then washed with deionized water untila total of 2 L of eluate was collected. The deionized water was removedwith a rotary evaporator and the resultant intermediate was dried in avacuum oven overnight at 50° C.

The intermediate was then dissolved in anhydrous ethanol (1 L) in around bottom flask fitted with a magnetic stir bar, a condenser and ahose adapter that was attached to a source of nitrogen gas. Thissolution was stirred and heated overnight in an oil bath at 100° C. Anadditional 500 mL of ethanol was added to the flask and heating andstirring was continued for an additional 4 hours. The solution wasallowed to cool to room temperature and was neutralized with alcoholicKOH to the bromothymol blue endpoint. The product precipitated from thesolution and was isolated by vacuum filtration, washed with anhydrousethanol and dried overnight at room temperature to afford 75.1 g ofproduct.

Preparative Example 3 Preparation of 4-EthoxycarbonylbenzenesulfonylChloride

A round bottom flask, fitted with a magnetic stir bar and a hose adapterconnected to a source of nitrogen gas, was charged with a solution ofpotassium 4-ethoxycarbonylbenzenesulfonate (75.1 g) dissolved in a 3:1(v/v) mixture of acetonitrile (300 mL) and sulfolane (100 mL). As thesolution was stirred, POCl₃ (55 mL) was added slowly and the stirringmixture was heated at 75° C. under a nitrogen atmosphere for 3 hours.The heterogeneous reaction mixture was allowed to cool to roomtemperature and was then concentrated using a rotary evaporator. Theflask was then cooled in an ice bath and ice was added to the mixture inthe flask. The product crystallized as a white solid and was filteredand washed with cold deionized water. The product was dried under vacuumat room temperature and 3 mmHg for 2 hours to afford 76 g of whitesolid.

Preparative Example 4 Preparation of 1-Chlorosulfonylanthraquinone

Sodium anthraquinone-1-sulfonate (50.0 g) was combined with POCl₃ (31mL) and a 1:2 (v/v) mixture of sulfolane (100 mL) and acetonitrile (200mL). The mixture was stirred and heated to 110° C. under a nitrogenatmosphere for 44 hours. The mixture was allowed to cool to roomtemperature and was then further cooled in a refrigerator. The mixturewas filtered and the filtrate was poured onto ice in a beaker and thismixture was stirred for 1 hour. The brown precipitate was filtered,washed with deionized water, dried in air and then further driedovernight in a vacuum oven at 45° C. and less than 1 mmHg pressure togive 12.08 g of the product as a brown solid.

Preparative Examples 5-8 Preparation of Substituted Alkali MetalBenzenesulfinates

Substituted alkali metal benzenesulfinates were prepared by hydrolysisof the substituted benzenesulfonyl chlorides that were obtainedcommercially or were prepared as described in Preparative Examples 1 and3. Each substituted benzenesulfonyl chloride was stirred for 3 hours at75° C. in deionized water, at a concentration of 0.2 g of substitutedbenzenesulfonyl chloride per milliliter of deionized water, with 2.5equivalents of Na₂SO₃ and 2.5 equivalents of NaHCO₃ in a round bottomflask. Each reaction mixture was then allowed to cool to roomtemperature and was then cooled in a refrigerator to 10° C. Each coldsolution was acidified with concentrated sulfuric acid until the pH wasless than 1.

Each precipitated solid was extracted into ethyl acetate and then theorganic phase was evaporated to dryness using a rotary evaporator toafford the substituted benzenesulfinic acid as a colorless solid. Eachof the solid substituted benzenesulfinic acids was dissolved in methanolto give approximately 10 weight percent solutions. Deionized water wasthen added dropwise to each solution until a precipitate just formed.Sufficient methanol was then added to the solution until all of thesolid dissolved. Each aqueous methanol solution was neutralized with a1M aqueous solution of an alkali metal hydroxide (MOH), as indicated inTable 1, to afford the substituted alkali metal substitutedbenzenesulfinate salts, which were isolated by removal of the solventwith a rotary evaporator. TABLE 1 Preparative Examples 5-8 Benzene- Wt.Benzene- Wt. Preparative sulfonyl sulfonyl Benzene- Example chloridechloride MOH sulfinate 5 4-Cyano 11.68 g  NaOH 9.30 g 6 4-Ethoxycarbonyl6.46 g LiOH 3.17 g 7 4-Chloro 5.11 g LiOH 3.06 g 8 4-Trifluoromethyl6.20 g NaOH 4.15 g

Preparative Example 9 Preparation of1-methoxy-4-(2-ethylhexyloxy)benzene

A mixture of 4-methoxyphenol (100.0 g), dry potassium carbonate (166.7g), acetonitrile (800 mL), and 2-ethylhexyl bromide (173.8 g) wasstirred mechanically and heated at reflux for 4 days. The mixture wasthen allowed to cool to room temperature and was diluted with 1.5 L ofdeionized water, after which the organic phase was separated. Theaqueous phase was extracted with hexane, and the combined organic layerswere washed two times with a 1.0 moles/liter aqueous solution of NaOHand were then dried over MgSO₄. The solvent was removed under reducedpressure to give an orange oil. The crude product was distilled underreduced pressure to give 152 g of a clear oil (bp 135-138° C. at 0.4mmHg).

Preparative Example 10 Preparation of2.5-bis(bromomethyl)-1-methoxy-4-(2-ethylhexyloxy)benzene

A mixture of the product from Preparative Example 9 (50.0 g),paraformaldehyde (30.0 g), acetic acid (100 mL) and HBr (30% in aceticacid, 100 mL) was heated with stirring to 70° C. The reactionspontaneously warmed to 80° C. and the paraformaldehyde dissolvedcompletely to give an orange solution. The mixture was heated andstirred for 4 hours at 70° C., after which time the reaction was cooledto room temperature. The mixture was diluted with methylene chloride(500 mL), the organic layer was separated, washed three times withdeionized water, once with saturated NaHCO₃, and was then dried overMgSO₄. Solvent removal under reduced pressure afforded a pale yellowsolid that was recrystallized from hexane to give 71.6 g of a lightyellow powder.

Preparative Example 11 Preparation of2-(2-ethylhexoxy)-5-methoxy-1,4-bis(benzyl)phosponate

A mixture of the product from Preparative Example 10 (28.26 g) andtriethyl phosphite (37.4 g) was stirred and heated to reflux for 6 h.After cooling, the product was heated under high vacuum to removeresidual triethylphosphite. A thick oil was obtained which slowlycrystallized after several days and was used without furtherpurification.

Preparative Example 12 Preparation ofbis-[4-(Diphenylamino)stryl]-1-(2-ethylhexyloxy)-4-(methoxy)benzene(KL68 Dye)

To a mixture of the product from Preparative Example 11 (11.60 g),4-diphenylaminobenzaldehyde (12.34 g), and dry tetrahydrofuran (400 mL),a 1.0M solution of potassium tert-butoxide in tetrahydrofuran (44 mL)was added dropwise as the mixture was stirred. This mixture was stirredfor 3 hours at room temperature, then the solvent was removed undervacuum. Deionized water (100 mL) was added to the residue, and themixture was extracted several times with methylene chloride. Thecombined organic layers were washed with saturated aqueous NaCl, driedover MgSO₄ and then the solvent was removed under vacuum. The crudeproduct was purified by column chromatography on silica gel using 30/70(v/v) methylene chloride/hexane as the mobile phase. Solvent removalusing a rotary evaporator afforded 14.44 g the product as a bright greensolid.

Preparative Example 13 Preparation of N,N-Dimethylmorpholinium Hydroxide

To a stirred solution of N-methylmorpholine (10.0 g) in1,2-dichloroethane (125 mL) at room temperature there was added methyliodide (14.1 g). The colorless precipitate that formed was filtered andwas washed sequentially with 1,2-dichloroethane and petroleum ether. Thesolid was dried in air at room temperature to afford 21.3 g of product.A sample of this product (1.0 g) was dissolved in deionized water (2 mL)and was passed through a column of strongly basic ion-exchange resin(available under the trade designation DOWEX 1X2-100 from Dow ChemicalCo., Midland, Mich.) that had been washed sequentially with 10 g of a10% aqueous solution of NaOH and 200 mL of deionized water. The samplewas washed from the column with 25 mL of deionized water. The elutedsolution was concentrated to dryness using a rotary evaporator and wasfurther dried using a vacuum oven at 50° C. overnight to give theproduct as a colorless solid.

Preparative Example 14 Preparation of1-Methyl-4-aza-1-azoniabicyclo[2.2.2]octane Hydroxide

To a stirred solution of 1,4-diazabicyclo[2.2.2]octane (10.0 g) in1,2-dichloroethane (100 mL) at room temperature there was added methyliodide (12.7 g). The colorless precipitate that formed was filtered andwas washed sequentially with 1,2-dichloroethane and petroleum ether. Thesolid was dried in air at room temperature to afford 21.3 g of product.All of this product was then dissolved in deionized water (200 mL) andwas stirred at room temperature while ammonium hexafluorophosphate (13.7g) was slowly added to the solution. The colorless precipitate thatformed was vacuum filtered and was washed with a small amount ofdeionized water. The solid was allowed to dry in air at room temperatureovernight and was further dried using a vacuum oven at 60° C. overnightto afford 7.1 g of product. A sample of this product (1.0 g) wasdissolved in deionized water (2 mL) and was passed through a column ofstrongly basic ion-exchange resin (available under the trade designationDOWEX 1X2-100 from Dow Chemical Co., Midland, Mich.) that had beenwashed sequentially with 10 g of a 10% aqueous solution of NaOH and 200mL of deionized water. The sample was washed from the column with 25 mLof deionized water. The eluted solution was concentrated to drynessusing a rotary evaporator and was further dried using a vacuum oven at50° C. overnight to give the product as a colorless solid.

Preparative Example 15 Preparation of 3-Ethyl-2-methylbenzoxazoliumChloride

A solution of 3-ethyl-2-methylbenzoxazolium iodide (1.0 g) in deionizedwater (20 mL) was passed through a column of ion-exchange resin(available under the trade designation DOWEX 1X2-100 from Dow ChemicalCo., Midland, Mich.) that had been washed sequentially with deionizedwater (200 mL), saturated aqueous NaCl (50 mL), and deionized water (200mL). The product was washed from the column with approximately 50 mL ofdeionized water and was concentrated to dryness using a rotaryevaporator to afford 0.73 g of product.

Preparative Examples 16-19 Preparation of Substituted TetrabutylammoniumBenzenesulfinates

Tetrabutylammonium benzenesulfinates were prepared from thecorresponding alkali metal sulfinates. Each alkali metal sulfinate wasdissolved in deionized water to give a 0.1M solution that was acidifiedwith concentrated sulfuric acid to afford the sulfinic acid as acolorless precipitate. Each mixture was extracted with ethyl acetate andthen the organic phase was evaporated to dryness using a rotaryevaporator. Each resultant solid was dissolved in 50% (v/v) aqueousmethanol and this solution was titrated with an aqueous solution oftetrabutylammonium hydroxide. Each mixture was evaporated to drynessusing a rotary evaporator to afford the product as a yellow oil. The ¹Hand ¹³C NMR spectra of each compound were consistent with the assignedstructure. Details of these preparations and oxidation and stabilitydata are given in Table 2. TABLE 2 Preparative Examples 16-19Preparative Example 16 17 18 19 Alkali Metal 4-Chloro 4-Ethoxy-4-Trifluoro- 4-Cyano Benzenesulfinate carbonyl methyl Wt. Alkali Metal0.50 g 0.58 g 1.72 g  2.00 g Benzenesulfinate Wt. 0.98 g 1.27 g 3.51 g 4.18 g Tetrabuylammonium Benzenesulfinate E_(ox) 0.09 V 0.11 V 0.18 V 0.15 V t_(1/2)(days)  138  174   88  >300

Preparative Example 20 Preparation of emim 4-Methylbenzenesulfinate

A mixture of sodium 4-methylbenzenesulfinate (3.1 g) and anhydrousethanol (80 mL) in a round bottom flask, fitted with a magnetic stirbar, was heated to approximately 75° C. with stirring. The mixture wasallowed to cool to approximately 40° C. and then a solution of1-ethyl-3-methylimidazolium chloride (2.0 g) in anhydrous ethanol (20mL) was added to the flask. The mixture was stirred for 2 hours afterwhich time it was filtered. The filtrate was concentrated to drynessusing a rotary evaporator to give a heterogeneous yellow oil which wastaken up in CHCl₃. This mixture was filtered and then the filtrate wasconcentrated to dryness using a rotary evaporator to afford 3.12 g ofthe product as a yellow oil.

Preparative Example 21 Preparation of Tetraphenylphosphonium4-Cyanobenzenesulfinate

A solution of sodium 4-cyanobenzenesulfinate (1.0 g) in anhydrousethanol (100 mL) was prepared in a 250 mL Erlenmeyer flask by heatingthe solution to boiling on a hot plate with magnetic stirring. To theboiling solution was added a hot solution of tetraphenylphosphoniumchloride (1.98 g) in anhydrous ethanol (50 mL) with constant stirring.The stirring solution was allowed to cool for 30 minutes, during whichtime a colorless precipitate appeared. The flask was then cooled in anice-bath for an additional 30 minutes with stirring. The mixture wasvacuum filtered and the filtrate was dried using a rotary evaporator toyield a deep yellow oil that contained some solid material. This residuewas dissolved in chloroform (50 mL) and the mixture was stirred for 20minutes and was then vacuum filtered. The deep yellow solution wasconcentrated to dryness using a rotary evaporator to afford a clearyellow oil that was further dried under vacuum for 1 hour at 3 mmHg toyield 2.20 g of the product as a bright yellow wax.

Preparative Example 22 Preparation of TetrabutylammoniumAnthraquinone-1-sulfinate

A solution of 1-chlorosulfonylanthraquinone (12.05 g) was combined withdeionized water (200 mL), Na₂SO₃ (18.34 g) and NaHCO₃ (12.22 g) in around bottom flask. The mixture was stirred and heated under a nitrogenatmosphere at 65° C. for 2 hours. The solution was then allowed to coolto room temperature and was then further cooled in a refrigerator. Theprecipitated solid that formed was isolated by filtration and wasallowed to dry in air. The solid was transferred to a flask to which wasadded 200 mL of a 2:1 (v/v) mixture of methanol and deionized water. Thesolution was titrated with 40% aqueous tetrabutylammonium hydroxideuntil a deep red color persisted. The solvent was removed with a rotaryevaporator and the deep red oil was dried under high vacuum for 2 daysat 45° C. to afford 16.98 g of product.

Preparative Example 23 Preparation of TetrabutylammoniumNaphthalene-1-sulfinate

A round bottom flask was charged with 1-naphthalenesulfonyl chloride(20.0 g), Na₂SO₃ (33.36 g), NaHCO₃ (22.24 g) and deionized water (350mL). The mixture was stirred and heated to 65° C. under a nitrogenatmosphere for 2 hours, after which time the mixture was allowed to coolto room temperature and was then further cooled in a refrigerator. Thecold mixture was acidified with concentrated H₂SO₄ which resulted in theformation of a precipitate. The mixture was extracted three times with100 mL of ethyl acetate. The organic extracts were combined and thesolvent was removed with a rotary evaporator to give a colorless solidthat was then dissolved in 240 mL of 1:1 (v/v) methanol-deionized waterin a beaker. The solution was titrated with a solution of 40% aqueoustetrabutylammonium hydroxide until the pH of the solution was 7.2. Thesolvent was removed with a rotary evaporator and the product was furtherdried in a vacuum oven at room temperature to afford 36.4 g of a yellowwaxy solid.

Preparative Example 24 Preparation of TetrabutylammoniumNaphthalene-2-sulfinate

A round bottom flask was charged with 2-naphthalenesulfonyl chloride(24.73 g), Na₂SO₃ (41.25 g), NaHCO₃ (41.25 g) and 350 mL deionizedwater. The mixture was stirred and heated to 65° C. under a nitrogenatmosphere for 2 hours, after which time the mixture was allowed to coolto room temperature and was then further cooled in a refrigerator. Thecold mixture was acidified with concentrated H₂SO₄, which resulted inthe formation of a precipitate.

The mixture was extracted three times with 100 mL of ethyl acetate. Theorganic extracts were combined and the solvent was removed with a rotaryevaporator to give a colorless solid that was then dissolved in 240 mLof 1:1 (v/v) methanol-deionized water in a beaker. The solution wastitrated with a solution of 40% aqueous tetrabutylammonium hydroxideuntil the pH of the solution was 7.2. The solvent was removed with arotary evaporator and the product was further dried in a vacuum oven atroom temperature to afford 46.9 g of a yellow waxy solid.

Preparative Example 25 Preparation of N,N-Dimethylmorpholinium4-Cyanobenzenesulfinate

Concentrated sulfuric acid was slowly added to a solution of sodium4-cyanobenzenesulfinate (0.15 g) in deionized water (10 mL). Aprecipitate formed and sulfuric acid was added dropwise until itappeared that no more precipitate was forming. The mixture was extractedtwice with ethyl acetate (20 mL) and the combined organic phases wereconcentrated to dryness using a rotary evaporator. The resultant solidwas dissolved in 50 weight percent aqueous methanol and this solutionwas titrated with a solution of N,N-dimethylmorpholinium hydroxide (0.85g) in deionized water (5 mL). The solution was concentrated to drynessusing a rotary evaporator and was further dried using a vacuum oven atroom temperature overnight. The resultant solid was then dissolved indeionized water and this solution was extracted twice with ethyl acetate(20 mL). The combined organic phases were concentrated to dryness usinga rotary evaporator. The resultant solid was further dried using avacuum oven overnight at room temperature to afford 0.24 g of product asa yellow oil.

Preparative Example 26 Preparation of1-Methyl-4-aza-1-azoniabicyclo[2.2.2]octane 4-Cyanobenzenesulfinate

Concentrated sulfuric acid was slowly added to a solution of sodium4-cyanobenzenesulfinate (0.25 g) in deionized water (10 mL). Aprecipitate formed and sulfuric acid was added dropwise until itappeared that no more precipitate was forming. The mixture was extractedtwice with ethyl acetate (20 mL) and the combined organic phases wereconcentrated to dryness using a rotary evaporator. The resultant solidwas dissolved in 50 weight percent aqueous methanol and this solutionwas titrated with a solution of the product of Preparative Example 14(0.27 g) in deionized water (5 mL) to a pH of approximately 7.2. Thesolution was concentrated to dryness using a rotary evaporator and wasfurther dried using a vacuum oven at room temperature overnight toafford 0.45 g of product as a yellow waxy solid.

Preparative Example 27 Preparation of N-Hexadecylpyridinium4-Cyanobenzenesulfinate

A solution of N-hexadecylpyridinium chloride (1.6 g) in ethanol (20 mL)was added to an Erlenmeyer flask containng a magnetically stirredboiling solution of sodium 4-cyanobenzenesulfinate (1.0 g) in anhydrousethanol (200 mL). The mixture was allowed to cool to room temperatureand was then further cooled in an ice bath. The mixture was filtered andthe filtrate was concentrated to dryness using a rotary evaporator. Theresidue was then dissolved in chloroform (100 mL), filtered, andconcentrated to dryness using a rotary evaporator to afford 2.4 g ofproduct.

Preparative Example 28 Preparation of 3-Ethyl-2-methylbenzoxazolium4-Cyanobenzenesulfinate

A solution of 3-ethyl-2-methylbenzoxazolium chloride (0.73 g) in ethanol(20 mL) was added to an Erlenmeyer flask containing a magneticallystirred boiling solution of sodium 4-cyanobenzenesulfinate (0.1 g) inanhydrous ethanol (20 mL). The mixture was allowed to cool to roomtemperature and was then further cooled in an ice bath. The mixture wasfiltered and the filtrate was concentrated to dryness using a rotaryevaporator. The residue was mixed with deionized water and this mixturewas extracted with ethyl acetate (2×20 mL). The combined organicextracts were concentrated to dryness using a rotary evaporator. Theresultant solid was then dissolved in methylene chloride, filtered andevaporated to dryness using a rotary evaporator to afford 0.08 g ofproduct.

Examples 1-3 Photocuring of 4-HBA Using Arylsulfinate Salts, MethyleneBlue and Diphenyliodonium Hexafluorophosphate

A stock solution of 4-HBA and methylene blue was prepared by dissolvingmethylene blue in 4-HBA to provide a solution that was lightly colored.Sufficient diphenyliodonium hexafluorophosphate was added to form asolution having 1 weight percent of the iodonium salt. Screw-cap vialswere charged with approximately 1 g of this solution. An amount of anarylsulfinate salt was added to each vial to give a salt concentrationof 1 weight percent. Each solution was purged with nitrogen gas for 45seconds after which time the vials were sealed. Each solution wasirradiated with 100 W quartz-tungsten-halogen (QTH) light source (modelI-100, available Cuda Fiberoptics, Jacksonville, Fla.) by holding andslowly agitating each vial approximately 2 cm in front of the lightsource. The light source shutter was fully open. Cure time wasconsidered to be the time that it took for the solution to no longerflow in the vial as the vial was agitated. The results are given in theTable 3. TABLE 3 Curing of Examples 1-3 Cure Time Example ArylsulfinateSalt (sec) 1 Tetrabutylammonium Anthraquinone-1-sulfinate  6 2Tetrabutylammonium Naphthalene-1-sulfinate <2 3 TetrabutylammoniumNaphthalene-2-sulfinate <2

Examples 4-15 Photocuring of HEA using Tetrabutylammonium4-Cyanobenzenesulfinate with Diphenyliodonium Hexafluorophosphate

To a stock solution of HEA and 1 weight percent tetrabutylammonimum4-cyanobenzenesulfinate there was added sufficient diphenyliodoniumhexafluorohosphate to give a solution having 1 weight percent of theiodonium salt. Screw-cap vials were charged with approximately 1 g ofthis solution. An amount of a dye was added to each vial to give a dyeconcentration sufficient to provide a lightly colored solution,typically between 50 and 1000 ppm, depending on the dye. Each solutionwas purged with nitrogen gas for 30 seconds after which time the vialswere sealed. Each solution was irradiated as described in Examples 1-3.The results are given in Table 4. TABLE 4 Curing of Examples 4-15 Curetime Uncured Example Dye (sec) color Cured Color 4 Methylene Green 2Green Colorless 5 Fluorescein 4 Green- Green yellow 6 Methylene blue 4Blue Pale yellow 7 Rose bengal 4 Red Pale red 8 Acridine orange 6 OrangeOrange 9 Methylene violet 7 Violet Red-violet 10 Rhodamine 6G 7 PinkPink 11 Cyanine 1 9 Blue-green Blue-violet 12 Basic Blue 3 10 Blue Blue13 Coumarin 153 Yellow Yellow 14 Nile Blue Chloride 10 Blue Blue 15Methyl Orange 70 Orange Orange

Examples 16-20 Photocuring of 4-HBA Using 4-Cyanobenzenesulfinates withDiphenyliodonium Hexafluorophosphate and Methylene Blue

To approximately 1 g each of solutions 4-HBA and 1 weight percent of the4-cyanobenzenesulfinate salts of Preparative Examples 21, 25, 26, 27,and 28 in individual screw cap vials there was added sufficientdiphenyliodonium hexafluorophosphate to give a solution comprising 1weight percent of the iodonium salt. An amount of methylene blue wasadded to each vial to give a dye concentration sufficient to providelightly colored solutions. Each solution was purged with nitrogen gasfor 1 minute after which time the vials were sealed. Each solution wasirradiated as described in Examples 1-3. The results are given in Table5. TABLE 5 Curing of Examples 16-20 Example 4-Cyanobenzenesulfinate saltCure time (sec) 16 Tetraphenylphosphonium <4 17 N,N-Dimethylmorpholinium<4 18 1-Methyl-4-aza-1-azoniabicylco[2.2.2]octane <4 19N-Hexadecylpyridinium <4 20 3-Ethyl-2-methylbenzoxazolium <3

Examples 21-24 Photocuring of 4-HBA Using Substituted BenzenesulfinatesAnd Basic Blue 3

Mixtures 4-HBA (0.5 g) with 1 weight percent diphenyliodoniumhexafluorophosphate, 20 ppm of Basic Blue 3, and 27 micromoles per gramof the substituted tetrabutylammonium benzenesulfinates of PreparativeExamples 16-19 were prepared. Each sample was evaluated for rate andextent of cure by photo differential scanning calorimetry (photo-DSC)using a model DSC2920 calorimeter (available from TA Instruments, NewCastle, Del.) with actinic radiation lower in energy than 300 nm at anirradiance of 20 mW/cm². The results are given in Table 6. TABLE 6Curing of Examples 21-24 Substituted Initial Time to peak Totaltetrabutylammonium Slope maximum evolved Example benzenesulfinate(W/g-min) (min) heat (J/g) 21 4-Chloro 94.1 0.25 438.7 224-Ethoxycarbonyl 115.1 0.24 509.2 23 4-Trifluoromethyl 86.9 0.27 501.124 4-Cyano 121.4 0.24 509.8

Examples 25-28 Photocuring of 4-HBA Using Substituted Arylsulfinates AndKL68 Dye

Mixtures of 0.5 g 4-HBA with 1 weight percent diphenyliodoniumhexafluorophosphate, 71 ppm of KL68 Dye and 1 weight percent of each ofthe substituted tetrabutylammonium benzenesulfinates of PreparativeExamples 16-19 were prepared. Each sample was evaluated for rate andextent of cure by photo differential scanning calorimetry as describedin Examples 21-24. The results are given in the Table 7. TABLE 7 Curingof Examples 25-28 Substituted Initial Time to peak Totaltetrabutylammonium Slope maximum evolved Example benzenesulfinate(W/g-min) (min) heat (J/g) 25 4-Chloro 94.4 0.26 487.0 264-Ethoxycarbonyl 125.7 0.24 522.3 27 4-Trifluoromethyl 116.6 0.24 516.128 4-Cyano 152.3 0.21 518.1

Examples 29-32 Photocuring of 4-HBA Using A Substituted BenzenesulfinateAnd Near-IR Dyes

Mixtures of 4-HBA (5.0 g) with 1 weight percent diphenyliodoniumhexafluorophosphate, 1 weight percent of the product of PreparativeExample 17 and approximately 0.1 weight percent of either near-IR dyeIR140 or near-IR dye IR780 iodide were prepared in screw-cap vials. Thesolutions were purged with nitrogen gas and then each sample wasirradiated with a QTH light source as described in Examples 1-3.Separately, samples of the mixtures were purged with nitrogen gas andwere then irradiated with actinic radiation from a QTH light source thatwas filtered with a RG715 long pass filter (available from EscoProducts, Oak Ridge, N.J.). The results are given in Table 8. TABLE 8Examples 29-32 Example Near-IR Dye RG715 filter Cure time (sec) 29 IR140No 15 30 IR140 Yes >60 31 IR780 iodide No 8 32 IR780 iodide Yes 30

Examples 33-35 Thermal Polymerization of Acrylate Monomer

Compositions of SR238, SR339, or SR399, each with 1 weight percentdiphenyliodonium hexafluorophosphate and 1 weight percent of the productof Preparative Example 19 were prepared in screw-cap vials. The vialswere sealed and were allowed to stand in the dark at room temperature.The mixtures were periodically examined to assess the viscosity bymanually tipping the vials to observe the flow of the liquids.Polymerization time was considered to be the time until the mixture nolonger flowed in the vial. The results are given in Table 9. TABLE 9Examples 33-35 Example Monomer Polymerization time 33 SR238 <5 min 34SR339 <5 min 35 SR399 <5 min

Example 36 Thermal Polymerization of Trimethylolpropane Triacrylate

A mixture of SR351, 1 weight percent diphenyliodoniumhexafluorophosphate, and 1 weight percent of the product of PreparativeExample 19 was prepared in a screw-cap vial. The vial was sealed and wasallowed to stand in the dark at room temperature. The mixture wasperiodically examined to assess the viscosity by manually tipping thevials and observing the flow of the mixture. The polymerization time,considered to be the time until the mixture no longer flowed in thevial, was found to be less then 3 minutes.

Example 37 Thermal Polymerization of Trimethylolpropane Triacrylate

A mixture of SR351, 0.5 weight percent diphenyliodoniumhexafluorophosphate, and 0.5 weight percent of the product ofPreparative Example 18 was prepared in a screw-cap vial. The vial wassealed and was allowed to stand in the dark at room temperature. Themixture was periodically examined to assess the viscosity by manuallytipping the vials and observing the flow of the mixture. Thepolymerization time, considered to be the time until the mixture nolonger flowed in the vial, was found to be less then 5 minutes.

1. A composition comprising: an electron donor comprising anarylsulfinate salt having a anion of Formula IAr¹—SO₂ ⁻  I and a cation having at least one carbon atom and either apositively charged nitrogen atom or a positively charged phosphorusatom, said electron donor having an oxidation potential inN,N-dimethylformamide of 0.0 to +0.4 volts versus a silver/silvernitrate reference electrode, wherein Ar¹ is a substituted phenyl, anunsubstituted or substituted C₇₋₃₀ aryl, or an unsubstituted orsubstituted C₃₋₃₀ heteroaryl, said substituted Ar¹ having a substituentthat is an electron withdrawing group or an electron withdrawing groupin combination with an electron donating group; and an electron acceptorhaving a reduction potential in N,N-dimethylformamide of +0.4 to −1.0volts versus a silver/silver nitrate reference electrode.
 2. Thecomposition of claim 1, wherein the Ar¹ group of the arylsulfinate saltis anthryl, naphthyl, acenaphthyl, phenanthryl, phenanthrenyl,perylenyl, anthracenyl, anthraquinonyl, anthronyl, biphenyl, terphenyl,9,10-dihydroanthracenyl, or fluorenyl, said Ar¹ group beingunsubstituted or substituted with an electron withdrawing group or anelectron withdrawing group in combination with an electron donatinggroup.
 3. The composition of claim 1, wherein the Ar¹ group of thearylsulfinate salt is quinolinyl, isoquinolinyl, quinazolinyl,quinoxalinyl, cinnolinyl, benzofuranyl, benzomercaptophenyl,benzoxazolyl, benzothiazolyl, benzimidazolyl, indolyl, phthalazinyl,benzothiadiazolyl, benzotriazinyl, phenazinyl, phenanthridinyl,acridinyl, or indazolyl, said Ar¹ group being unsubstituted orsubstituted with an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group.
 4. Thecomposition of claim 1, wherein the Ar¹ group of the arylsulfinate saltis a substituted phenyl, an unsubstituted or substituted naphthyl, or anunsubstituted or substituted anthraquinonyl, said substituted Ar¹ havinga substituent that is an electron withdrawing group or an electronwithdrawing group in combination with an electron donating group.
 5. Thecomposition of claim 1, wherein the Ar¹ group is phenyl substituted withan electron withdrawing group selected from halo, cyano, fluoroalkyl,perfluoroalkyl, carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl,formyl, carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl,perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl,dialkylphosphonato, diarylphosphonato, aminocarbonyl, or combinationsthereof.
 6. The composition of claim 1, wherein the anion of thearylsulfinate salt is 4-chlorobenzenesulfinate, 4-cyanobenzenesulfinate,4-ethoxycarbonylbenzenesulfinate, 4-trifluoromethylbenzenesulfinate,3-trifluoromethylbenzenesulfinate, 1-anthraquinone sulfinate,1-naphthalenesulfinate, or 2-naphthalenesulfinate.
 7. The composition ofclaim 1, wherein the cation of the arylsulfinate salt is ring structurecomprising a 4 to 12 member heterocyclic group having a positivelycharged nitrogen atom, said heterocyclic being saturated or unsaturatedand having up to 3 heteroatoms selected from oxygen, sulfur, nitrogen,or combinations thereof, wherein said ring structure is unsubstituted orsubstituted with a substituent selected from an alkyl, aryl, acyl,alkoxy, aryloxy, halo, mercapto, amino, hydroxy, azo, cyano, carboxy,alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, or combinations thereof.8. The composition of claim 7, wherein said heterocyclic group isbicyclic.
 9. The composition of claim 7, wherein said heterocyclic groupis fused to a cyclic or bicyclic group that is saturated or unsaturatedand that has 0 to 3 heteroatoms.
 10. The composition of claim 7, whereinsaid heterocyclic group is fused to an aromatic ring having 0 to 3heteroatoms.
 11. The composition of claim 1, wherein the cation of thearylsulfinate salt is of Formula II

where R¹ is an unsubstituted alkyl, an alkyl substituted with a hydroxy,an unsubstituted aryl, or an aryl substituted with an alkyl, hydroxy, orcombinations thereof; and each R⁴ is independently hydrogen, anunsubstituted alkyl, an alkyl substituted with a hydroxy, anunsubstituted aryl, or an aryl substituted with an alkyl, hydroxy orcombination thereof.
 12. The composition of claim 1, wherein the cationof the arylsulfinate salt is of Formula III

where each R² is independently an unsubstituted alkyl, an alkylsubstituted with a hydroxy, an unsubstituted aryl, or an arylsubstituted with an alkyl, hydroxy, or combinations thereof.
 13. Thecomposition of claim 1, wherein the cation of the arylsulfinate salt isa tetraalkylammonium ion.
 14. The composition of claim 1, wherein thecation of the arylsulfinate salt is a tetrabutylammonium ion.
 15. Thecomposition of claim 1, wherein the arylsulfinate salt has an anion thatis a benzenesulfinate substituted with an electron withdrawing groupelectron selected from halo, cyano, fluoroalkyl, perfluoroalkyl,carboxy, alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl,carbonyl, sulfo, alkoxysulfonyl, aryloxysulfonyl,perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl, alkynyl,dialkylphosphonato, diarylphosphonato, aminocarbonyl, or combinationsthereof and the cation is a tetraalkylammonium ion.
 16. The compositionof claim 1, wherein the electron donor is tetrabutylammonium4-ethoxycarbonylbenzenesulfinate or tetrabutylammonium4-cyanobenzenesuflinate.
 17. The composition of claim 1, wherein theelectron acceptor is an iodonium salt, a hexaarylbisimidizole, apersulfate, a peroxide, or a metal ion in an oxidized state.
 18. Thecomposition of claim 1, further comprising a sensitizing compoundcapable of absorbing a wavelength of actinic radiation in the range of250 to 1000 nanometer.
 19. The composition of claim 18, wherein theelectron acceptor is a diaryliodonium salt, a hexaarylbisimidizole, orcombinations thereof.
 20. The composition of claim 18, wherein theelectron acceptor has an electron potential in the range of 0.0 to −1.0volts versus a silver/silver nitrate reference electrode.
 21. Thecomposition of claim 1, further comprising an ethylenically unsaturatedmonomer.
 22. The composition of claim 21, wherein the ethylenicallyunsaturated monomer comprises a monoacrylate, monomethacrylate,diacrylate, dimethacrylate, polyacrylate, polymethacrylate, orcombinations thereof, wherein said monomer is unsubstituted orsubstituted with a hydroxy.
 23. The composition of claim 18, wherein thecomposition further comprises a hydroxy-containing material selectedfrom an alcohol, a hydroxy-containing monomer, or combinations thereof.24. A method of photopolymerization comprising irradiating aphotopolymerizable composition with actinic radiation until thephotopolymerizable composition gels or hardens, said photopolymerizablecomposition comprising: an ethylenically unsaturated monomer; asensitizing compound capable of absorbing a wavelength of actinicradiation in the range of 250 to 1000 nanometers; an electron donorhaving an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4volts versus a silver/silver nitrate reference electrode, said electrondonor comprising an arylsulfinate salt having an anion of Formula IAr¹—SO₂ ⁻  I and a cation comprising at least one carbon atom and eithera positively charged nitrogen atom or a positively charged phosphorusatom, wherein Ar¹ is a substituted phenyl, an unsubstituted orsubstituted C₇₋₃₀ aryl, or an unsubstituted or substituted C₃₋₃₀heteroaryl, said substituted Ar¹ having a substituent that is anelectron withdrawing group or an electron withdrawing group incombination with an electron donating group; and an electron acceptorhaving a reduction potential in N,N-dimethylformamide of +0.4 to −1.0volts versus a silver/silver nitrate reference electrode, said electronacceptor being colorless when dissolved in an alcohol or theethylenically unsaturated monomer.
 25. The method of claim 24, whereinthe anion of the arylsulfinate salt is 4-chlorobenzenesulfinate,4-cyanobenzenesulfinate, 4-ethoxycarbonylbenzenesulfinate,4-trifluoromethylbenzenesulfinate, 3-trifluoromethylbenzenesulfinate,1-anthraquinone sulfinate, 1-naphthalenesulfinate, or2-naphthalenesulfinate.
 26. The method of claim 24, wherein the cationof the arylsulfinate salt is a tetraalkylammonium ion.
 27. The method ofclaim 24, wherein the arylsulfinate salt has an anion that is abenzenesulfinate substituted with an electron withdrawing group electronselected from halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy,alkoxycarbonyl, aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo,alkoxysulfonyl, aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl,azo, alkenyl, alkynyl, dialkylphosphonato, diarylphosphonato,aminocarbonyl, or combinations thereof and the cation is atetraalkylammonium ion.
 28. The method of claim 24, wherein the electronacceptor is an iodonium salt, a hexaarylbisimidizole, or combinationsthereof.
 29. The method of claim 24, wherein the electron acceptor is adiaryliodonium salt.
 30. The method of claim 24, wherein thephotopolymerizable composition comprises 0.1 to 4 wt % electron donor,0.1 to 4 wt % electron acceptor, and 5 ppm to 4 wt % sensitizingcompound based on the weight of the monomer.
 31. The method of claim 24,wherein the ethylenically unsaturated monomer comprises ahydroxy-containing monomer.
 32. The method of claim 24, wherein thephotopolymerizable composition further comprises an alcohol.
 33. Amethod of polymerization comprising: forming a polymerizable compositioncomprising an ethylenically unsaturated monomer; an electron donorhaving an oxidation potential in N,N-dimethylformamide of 0.0 to +0.4volts versus a silver/silver nitrate reference electrode, said electrondonor comprising an arylsulfinate salt having an anion of Formula IAr¹—SO₂ ⁻  I and a cation that contains at least one carbon atom andeither a positively charged nitrogen atom or a positively chargedphosphorus atom, wherein Ar¹ is a substituted phenyl, an unsubstitutedor substituted C₇₋₃₀ aryl, or an unsubstituted or substituted C₃₋₃₀heteroaryl, said substituted Ar¹ having a substituent that is anelectron withdrawing group or an electron withdrawing group incombination with an electron donating group; an electron acceptor havinga reduction potential in N,N-dimethylformamide of +0.4 to −1.0 voltsversus a silver/silver nitrate reference electrode; and reacting thepolymerizable composition.
 34. The method of claim 33, wherein theelectron acceptor is a persulfate, a peroxide, a metal ion in anoxidized state, or a combination thereof.
 35. The method of claim 34,wherein said reacting comprises applying heat.
 36. The method of claim33, wherein the anion of the arylsulfinate salt is4-chlorobenzenesulfinate, 4-cyanobenzenesulfinate,4-ethoxycarbonylbenzenesulfinate, 4-trifluoromethylbenzenesulfinate,3-trifluoromethylbenzenesulfinate, 1-anthraquinone sulfinate,1-naphthalenesulfinate, or 2-naphthalenesulfinate.
 37. The method ofclaim 33, wherein the arylsulfinate salt has an anion that is abenzenesulfinate substituted with an electron withdrawing group selectedfrom halo, cyano, fluoroalkyl, perfluoroalkyl, carboxy, alkoxycarbonyl,aryloxycarbonyl, halocarbonyl, formyl, carbonyl, sulfo, alkoxysulfonyl,aryloxysulfonyl, perfluoroalkylsulfonyl, alkylsulfonyl, azo, alkenyl,alkynyl, dialkylphosphonato, diarylphosphonato, aminocarbonyl, orcombinations thereof and the cation is a tetraalkylammonium ion.
 38. Themethod of claim 33, wherein the polymerizable composition comprises 0.1to 4 wt % electron donor and 0.1 to 4 wt % electron acceptor based onthe weight of the ethylenically unsaturated monomer.
 39. The method ofclaim 33, wherein the polymerizable composition further comprises asensitizing compound and said reacting comprises exposing thepolymerizable composition to actinic radiation having a wavelength inthe range of 250 to 1000 nanometers.